3, 


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I 


I 


A 


COMPENDIOUS  SYSTEM 

O F 

ANATOMY. 

IN  SIX  PA.RTS. 


Part  I.  Osteology. 

II.  Of  the  Muscles, 

ETC. 

III.  Of  the  Abdomen. 


Part.  IV.  Of  the  Thorax. 

V.  Of  the  Brain 

and  Nerves. 

VI.  Of  the  senses. 


ILLUSTRATED  WITH  TWELVE  LARGE  COPPERPLATES. 


EXTRACTED  from  the  American  CBlsition 
OF  THE  ENCYCLOP.(E,DlA. 

NOW  PUBLISHING, 

BY  THOMAS  DOBSON,  AT  TllE  STONE  HOUSE,  N®  41, 
SECOND  STREET,  PHILADELPHIA. 

M DCCilCII. 


J- 

e 


/ 

i 


9. 


I 


A 


SYSTEM! 

O F 

ANATOMY. 


z 


Anatomy  is  the  art  of  difle^ting,  or  arti- 
ficially feparating  and  taking  to  pieces,  the 
different  parts  of  the  human  body,  in  order  to  an 
exa£t  difcovery  of  their  fituation,  ftrudure  and 
oeconomy.  The  word  is  Greek,  derived 

from  to  diffed,  or  feparate  by  Cutting. 

INTRODUCTION. 

§ I.  Hijlory  of  Anatomy. 

This  art  feems  to  have  been  very  ancient; 
though,  for  a long  time,  known  only  in  an  im- 
perfedt  manner. — The  firft  men  who  lived  muft 

A 2 have 


4 INTRODUCTION, 

have  foon  acquired  fome  notions  of  the  ftrudure 
of  their  own  bodies,  particularly  of  the  external 
parts,  and  of  fome  even  of  the  internal,  fuch  as 
bones,  joints,  and  finews,  which  are  expofed 
to  the  examination  of  the  fenfes  in  living  bodies. 

This  rude  knowledge  mull  have  been  gradu- 
ally improved,  by  the  accidents  to  which  che 
body  is  expofed,  by  the  neceffities  of  life,  and 
by  the  various  cuftoms,  ceremonies,  and  fuper- 
ftitions,  of  different  nations.  'I'hus,  the  obferv- 
ance  of  bodies  killed  by  violence,  attention  to 
wounded  men,  and  to  many  difeafes,  the  vari- 
ous ways  of  putting  criminals  to  death,  the  fune- 
ral ceremonies,  and  a variety  of  fuch  things,  muft 
have  fhown  men  every  day  more  and  more  of 
themfelves ; efpecially  as  curiofity  and  felf-love 
would  here  urge  them  powerfully  to  obfervation 
and  reflection. 

The  brute-creation  having  fuch  an  affinity  to 
man  in  outward  form,  motions,  fenfes,  and  ways 
of  life ; the  generation  of  the  fpecies,  and  the 
effect  of  death  upon  the  body,  being  obferved 
to  be  fo  nearly  the  fame  in  both  ; the  conclufion 
was  not  only  obvious,  but  unavoidable,  that  their 
bodies  were  formed  nearly  upon  the  fame  model. 
And  the  opportunities  of  examining  the  bodies 
of  brutes  were  fo  eafily  procured,  indeed  fo  ne- 
ceiTarily  occurred  in  the  common  bufmefs  of 
life,  that  the  huntfman  in  making  ufe  of  his 
prey,  the  priefl  in  facrificing,  the  augur  in  di- 
vination, and,  above  all,  the  butcher,  or  thofe 

who 


INTRODUCTION.  5 

who  might  out  of  curiofity  attend  upon  his  ope-= 
rations,  muft  have  been  daily  adding  to  the  little 
flock  of  anatomical  knowledge.  Accordingly 
we  find,  in  fa£t,  that  the  South-fea-iflanders,  who 
have  been  left  to  their  own  obfervation  and  rea- 
foning,  without  the  alfiftance  of  letters,  have 
yet  a confiderable  lhare  of  rude  or  wild  anatomi- 
cal and  phyfiological  knowledge.  -Dr  Hunter 
informs  us,  that  when  Omai  was  in  his  mufeum 
with  Mr  Banks,  though  he  could  not  explain 
himfelf  intelligibly,  they  plainly  faw  that  he 
knew  the  principal  parts  of  the  body,  and  fome- 
thing  likewife  of  their  ufes  ; and  manifefled  a 
great  curiofity  or  defire  of  having  the  funftions 
of  the  internal  parts  of  the  body  explained  to 
him  ; particularly  the  relative  functions  of  the 
two  fexes,  which  with  him  feemed  to  be  the  moft 
interefting  objed;  of  the  human  mind. 

We  may  further  imagine,  that  the  Philofo- 
phers  of  the  moft  early  ages,  that  is,  the  men 
of  curiofity,  obfervation,  experience  and  reflec- 
tion, could  not  overlook  an  inftance  of  natural 
organization,  which  was  fo  interefting,  and  at  the 
fame  time  fo  wonderful,  more  efpecially  fuch  of 
them  as  applied  to  the  ftudy  and  cure  of  difeafes. 
We  know  that  phyfic  was  a branch  of  philofo- 
phy  till  the  age  of  Hippocrates. 

Thus  the  art  muft  have  been  circumftanced  in 
its  beginning.  We  lhall  next  fee  from  the  tef- 
timony  of  hiftorians  and  other  writers,  how  it 
adually  appeared  as  an  art,  from  the  time  that 

writing 


6 INTRODUCTION, 

writing  was  introduced  among  men ; how  it  waf 
improved  and  conveyed  down  to  us  through  a 
long  feries  of  ages. 

Civilization,  and  improvements  of  every  kind, 
would  naturally  begin  in  fertile  countries  and 
healthful  climates,  where  there  would  be  leifure 
for  reflection,  and  an  appetite  for  amufement. 
Accordingly,  writing,  and  many  other  ufeful 
and  ornamental  inventions  and  arts,  appear  to 
have  been  cultivated  in  the  eaftern  parts  of  Afia 
long  before  the  earlieft  times  that  are  treated  of 
by  the  Greek  or  other  European  writers  ; and 
that  the  arts  and  learning  of  thofe  eaftern  people 
were  in  fubfequent  times  gradually  communi- 
cated to  adjacent  countries,  efpecially  by  the  me- 
dium of  traffic.  The  cuftoms,  fuperftitions,  and 
climate  of  eaftern  countries,  however,  appear  to 
have  been  as  unfavorable  to  practical  anatomy, 
as  they  were  inviting  to  the  ftudy  of  aftronomy, 
geometry,  poetry,  and  all  the  fofter  arts  of  peace. 

Animal  bodies  there,  run  fo  quickly  into  nau- 
feous  putrefaction,  that  the  early  inhabitants  muft 
have  avoided  fuch  offenfive  employments,  as  ana- 
tomical inquiries,  like  their  pofterity  at  this  day. 
And,  in  fad:,  it  does  not  appear,  by  the  writ- 
ings of  the  Grecians,  or  Jews,  or  Phoenicians, 
or  of  other  eaftern  countries,  that  anatomy  was 
particularly  cultivated  by  any  of  thofe  eaftern  na- 
tions. In  tracing  it  backwards  to  its  infancy,  we 
cannot  go  farther  into  antiquity  than  the  times 
of  the  Grecian  philofophers.  As  an  art  in  the 

ftate 


INTRODUCTION.  7 

ftate  of  fome  cultivation,  it  may  be  faid  to  have 
been  brought  forth  and  bred  up  among  them  as 
a branch  of  natural  knowledge* 

The  sera  of  philofophy,  as  it  was  called,  be- 
gan with  Thales  the  Milefian  being  declared  by 
a very  general  confent  of  the  people,  the  moft 
wife  of  all  the  Grecians,  480  years  before  Chrift. 
The  philofophers  of  his  fchool,  which  was  called 
the  Ionian,  cultivated  principally  natural  know- 
ledge. Socrates,  the  feventh  in  fucceffion  of  their 
great  teachers,  introduced  the  ftudy  of  morals, 
and  was  thence  faid  to  bring  down  philofophy 
from  heaven,  to  make  men  truly  wife  and  hap- 

In  the  writings  of  his  fcholar  and  fuccelfor 
Plato,  we  fee  that  the  philofophers  had  carefully 
ccmfidered  the  human  body,  both  in  its  organi- 
zation and  funfhions  ; and  though  they  had  not 
arrived  at  the  knowledge  of  the  more  minute  and 
intricate  parts,  which  required  the  fucceffive  la- 
bour and  attention  of  many  ages,  they  had  made 
up  very  noble  and  comprehenfive  ideas  of  the 
fubjeft  in  general.  The  anatomical  defcriptions 
of  Xenophon  and  Plato  have  had  the  honour  of 
being  quoted  by  Longinus  (§  xxxii.)  as  fpeci- 
mens  of  fublime  writing  : and  the  extract  from 
Plato  is  ftill  more  remarkable  for  its  containing 
the  rudiments  of  the  circulation  of  the  blood. 
“ The  heart  (fays  Plato)  is  the  centre  or  knot  of 
the  blood-veifels  ; the  fpring  or  fountain  of  the 
blood  which  is  carried  impetuoufly  round  ; the 

blood 


8 INTRODUCTION. 

blood  is  the  pabulum  or  lood  of  the  flefh ; and, 

for  the  purpofe  of  nourifhment,  the  body  is  laid 

out  into  canals,  like  thofe  which  are  drawn 

through  gardens,  that  the  blood  maybe  conveyed, 

as  from  a fountain,  to  every  part  of  the  pervious 

body.” 

- Hippocrates  was  nearly  contemporary  with  the 
great  philofophers  of  whom  we  have  been  fpeak- 
ing,  about  400  years  before  the  Chriftian-  aera. 
He  is  faid  to  have  feparated  the  profeflion  of 
philofophy  and  phyfic,  and  to  have  been  the  firft 
who  applied  to  phyfic  alone  as  the  bufmefs  of 
his  life.  He  is  likewife  generally  fuppofed  to  be 
the  firft  who  wrote  upon  anatomy.  We  know 
of  nothing  that  was  written  exprefsly  upon  the 
fubjedt  before  ; and  the  firft  anatomical  dilfedHon 
which  has  been  recorded,  was  made  by  his  friend 
Democritus  of  Abdera. 

If,  however,  we  read  the  works  of  Hippo- 
crates with  impartiality,  and  apply  his  accounts 
of  the  parts  to  what  we  now  know  of  the  human 
body,  we  muft  allow  his  defcriptions  to  be  im- 
perfect, incorrect,  fometimes  extravagant,  and 
often  unintelligible,  that  of  the  bones  only  ex- 
cepted. He  feems  to  have  ftudied  thefe  with 
more  fuccefs  than  the  other  parts,  and  tells  us 
that  he  had  an  opportunity  of  feeing  a human 
fkeleton. 

From  Flippocrates  to  Galen,  who  fiourifhed 
towards  the  end  of  the  fecond  century,  in  the 
decline  of  the  Roman  empire,  that  is,  in  the 

fpace 


INTRODUCTION.  9 

fpace  of  600  years,  anatomy  was  greatly  im- 
proved ; the  philofophers  ftill  confidering  it  as  a 
moft  curious  and  interefting  branch  of  natural 
knowledge,  and  the  phyficians,  as  a principal 
foundation  of  their  art.  Both  of  them,  in  that 
interval  of  time,  contributed  daily  to  the  com- 
mon ftock,  by  more  accurate  and  extended  ob- 
fervations,  and  by  the  lights  of  improving  philo- 
fophy. 

As  thefe  two  great  men  had  applied  very  par- 
ticularly to  the  ftudy  of  animal  bodies,  they  not 
only  made  great  improvements,  efpecially  in 
phyfiology,  but  raifed  the  credit  of  natural 
knowledge,  and  fpread  it  as  wide  as  Alexander’s 
empire. 

Few  of  Ariftotle’s  writings  were  made  public 
in  his  lifetime.  He  affected  to  fay  that  they 
would  be  unintelligible  to  thofe  who  had  not 
heard  them  explained  at  his  ledtures  : and,  ex- 
cept the  ufe  which  Theophraftus  made  of  them, 
they  were  loft  to  the  public  for  above  130  years 
after  the  death  of  Theophraftus  j and  laft  came 
out  defedtive  from  bad  prefervation,  and  corrupt- 
ed by  men,  who,  v/ithout  proper  qualifications, 
prefumed  to  corredl  and  fupply  what  was  loft. 

From  the  time  of  Theophraftus,  the  ftudy  of 
natural  knowledge  at  Athens  was  forever  on  the 
decline  ; and  the  reputation  of  the  Lycseum  and 
Academy  was  almoft  confined  to  the  ftudies 
which  are  fubfervient  to  oratory  and  public 
fpeaking. 


The 


lO 


INTRODUCTION. 

ITe  other  great  inftitution  for  Grecian  edu- 
cation, was  at  Alexandria  in  Egypt.  The  firft 
Ptolemies,  both  from  their  love  of  literature, 
and  to  give  true  and  permanent  dignity  to  their 
empire,  and  to  Alexander’s  favorite  city,  fet  up 
a grand  fchool  in  the  palace  itfelf,  with  a mufeum 
and  library,  which,  we  may  fay,  has  been  the 
moT  famed  in  the  world.  Anatomy,  among 
other  fciences,  was  publicly  taught ; and  the  two 
diftinguidied  anatomifts  were  Erafiftratus  the  pu- 
pil and  friend  of  Theophraftus,  and  Herophilus. 
Their  voluminous  works  are  all  loft  ; but  they 
are  quoted  by  Galen  almoft  in  every  page.  Thefe 
profeffors  were  probably  the  firft  who  were  au- 
thorized to  difTed;  human  bodies  ; a peculiarity 
which  marks  ftrongly  the  philofophical  magnani- 
mity of  the  firft  Ptolemy,  and  fixes  a great  sera 
in  the  hiftory  of  anatomy.  And  it  was,  no  doubt, 
from  this  particular  advantage  which  the  Alex- 
andrians had  above  all  others,  that  their  fchool 
not  only  gained,  but  for  many  centuries  pre- 
ferved,  the  firft  reputation  for  medical  education. 
Ammianus  Marcelliims,  who  lived  about  650 
years  after  the  fciiools  w^ere  fet  up,  fays,  they  were 
lb  famous  in  his  time,  that  it  was  enough  to  fe- 
cure  credit  to  any  phyfician,  if  he  could  fay  he 
had  ftudied  at  Alexandria. 

Heroi^hilus  has  been  laid  to  have  anatomized 

i • 

700  bodies.  W e mull  allow  for  exaggeration. 
Kkiy,  it  was  faid,  that  both  he  and  Erafiftratus 
made  it  a common  practice  to  open  living  bodies, 

that 


INTRODUCTION.  ii 

that  they  might  difcover  the  more  fecret  fprings 
of  life.  But  this,  no  doubt,  was  only  a ^'Tligar 
opinion,  rifmg  from  the  prejudices  of  mankind ; 
and  accordingly,  without  any  good  reafon,  fuch 
tales  have  been  told  of  modern  anatomifts,  and 
have  been  believed  by  the  vulgar. 

Among  the  Romans,  though  it  is  probable  they 
had  phyhcians  and  furgeons  from  the  founda- 
tion of  the  city,  yet  we  have  no  account  of  any 
of  thefe  applying  themfelves  to  anatomy  for  a 
very  long  time.  Archagathus  was  the  hrft 
Greek  phyfician  eftablifhed  in  Rome,  and  he  was 
banifhed  the  city  on  account  of  the  feverity  of 
his  operations. — Afclepiades,  who  flourifhed  in 
Rome  I o I years  after  Archagathus,  in  the  time 
of  Pompey,  attained  fuch  a high  reputation  as 
to  be  ranked  in  the  fame  clafs  with  Hippocrates. 
He  feemed  to  have  fome  notion  of  the  air  in  res- 
piration acting  by  its  weight ; and  in  accounting 
for  digeftion,  he  fuppofed  the  food  to  be  no  far- 
ther changed  than  by  a comminution  into  ex- 
tremely fmall  parts,  which  being  diftributed  to 
the  Several  parts  of  the  body,  is  affimilated  to  the 
nature  of  each.  One  Caffius,  commonly  thought 
to  be  a difciple  of  Afclepiades,  accounted  for  the 
right  fide  of  the  body  becoming  paralytic  on 
hurting  the  left  fide  of  the  brain,  in  the  fame 
manner  as  has  been  done  by  the  moderns,  viz. 
by  the  croffing  of  the  nerves  from  the  right  to 
the  left  fide  of  the  brain. 

From  the  time  of  Afclepiades  to  the  fecond 

centurv. 


12 


INTRODUCTION, 
century,  phyficians  feem  to  have  been  greatly 
encouraged  at  Rome ; and,  in  the  writings  of 
Celfus,  Rufus,  Pliny,  Coelius,  Aurelianus,  and 
Arseteus,  we  find  feveral  anatomical  obfervations, 
but  moftly  very  fuperficial  and  inaccurate.  To- 
wards the  end  of  the  fecond  century  lived  Clau- 
dius Gallenus  Pergamus,  whofe  name  is  fo  well 
known  in  the  medical  world.  He  applied  him- 
felf  particularly  to  the  ftudy  of  anatomy,  and 
did  more  in  that  way  than  all  that  went  before 
him.  He  feems,  however,  to  have  been  at  a^ 
great  lofs  for  human  fubjedts  to  operate  Upon  ; 
and  therefore  his  defcription  of  the  parts  are 
moftly  taken  from  brute  animals.  His  works 
contain  the  fulleft  hiftory  of  anatomifts,  and  the 
moft  complete  fyftem  of  the  fcience,  to  be  met 
with  any  where  before  him,  or  for  feveral  cen- 
turies after ; fo  that  a number  of  paftages  in  them 
were  reckoned  abfolutely  unintelligible  for  many 
ages,  until  explained  by  the  difcoveries  of  fuc- 
ceeding  anatomifts. 

About  the  end  of  the  fourth  century,  Nimefi- 
us  bifhop  of  Emifia  wrote  a treatife  on  the  na- 
ture of  man,  in  which  it  is  faid  were  contained 
two  celebrated  modern  difcoveries  ; the  one,  the 
ufes  of  the  bile,  boafted  of  by  Sylvius  de  la  Boe ; 
and  the  other,  the  circulation  of  the  blood.  This 
laft,  however,  is  proved  by  Dr  Friend,  in  his 
Hiftory  of  phyfic,  p.  229.  to  be  falfely  afcribed 
to  this  author. 

The  Roman  empire  beginning  now  to  be  op- 

prefted 


INTRODUCTION.  13 

prefTed  by  the  barbarians,  and  funk  in  grofs  fu- 
peritition,  learning  of  all  kinds  decreafed  ; and 
when  the  empire  was  totally  overwhelmed  by 
thofe  barbarous  nations,  every  appearance  of 
fcience  was  almofl  extinguiflied  in  Europe.  The 
only  remains  of  it  were  among  the  Arabians  in 
Spain  and  in  Afia. — -The  Saracens  who  came  into 
Spain,  deftroyed  at  firft  all  the  Greek  books 
which  the  Vandals  had  fpared  : but  though  their 
government  Wc  s in  a conftant  ftruggle  and  fluc- 
tuation during  800  years  before  they  were  driven 
out,  they  received  a tafte  for  learning  from  their 
eountrymen  of  the  eaft ; feveral  of  their  princes 
encouraged  liberal  ftudies  ; public  fchools  were 
fet  up  at  Cordova,  Toledo,  and  other  towns, 
and  tranflations  of  the  Greeks  into  the  Arabic 
were  univerfally  in  the  hands  of  their  teachers. 

- Thus  was  the  learning  of  the  Grecians  trans- 
ferred to  the  Arabians.  But  though  they  had  fo 
good  a foundation  to  build  upon,  this  art  was  ne- 
ver improved  while  they  were  mafters  of  the 
world  ; for  they  were  fatisfied  with  commenting 
upon  Galen ; and  feem  to  have  made  no  diflec- 
tions of  human  bodies. 

Abdollaliph,  who  was  himfelf  a teacher  of 
anatomy,  a man  eminent  in  his  time  (at  and 
before  1203)  for  his  learning  and  curiofity;  a 
great  traveller,  who  had  been  bred  at  Bagdad, 
and  had  feen  many  of  the  great  cities  and  prin- 
cipal places  for  ftudy  in  the  Saracen  em.pire ; 
who  had  a favourable  opinion  of  original  obfer- 

vation, 


14  INTRODUCTION, 
vation,  in  oppofition  to  book-learning ; who 
boldly  corrected  fome  of  Galen’s  errors,  and 
was  perfuaded  that  many  more  might  be  detect- 
ed ; this  man,  we  fay,  never  made  or  faw,  or 
feemed  to  think  of  a human  diffeCtion.  He  dif- 
covered  Galen’s  errors  in  the  ofteology,  by  going 
to  burying-grounds,  with  his  ftudents  and  others, 
where  he  examined  and  demonftraced  the  bones  ; 
he  earneftly  recommended  that  method  of  Itudy, 
in  preference  even  to  the  reading  of  Galen,  and 
thought  that  many  further  improvements  might 
be  made  ; yet  he  feemed  not  to  have  an  idea  that 
a frefh  fubjeCl  might  be  diffeCted  with  that  view. 

Perhaps  the  Jewiih  tenets,  which  the  Maho- 
metans adopted,  about  uncleanlinels  and  pollu- 
tion, might  prevent  their  handling  dead  bodies  ; 
or  their  opinion  of  what  was  fuppofed  to  pafs 
between  an  angel  and  the  dead  perfon,  might 
make  them  think  difturbing  the  dead  highly  fa- 
crilegious.  Such,  howxver,  as  Arabian  learning 
was,  for  many  ages  together  there  was  hardly 
any  other  in  all  the  weftern  countries  of  Europe. 
It  was  introduced  by  the  eftablifhment  of  the 
Saracens  in  Spain  in  7 1 1 , and  kept  its  ground 
till  the  reftoration  of  learning  in  the  end  of  the 
15th  century.  The  ftate  of  anatomy  in  Europe, 
in  the  times  of  Arabian  influence,  may  be  feen 
by  reading  a very  fhort  fyftem  of  anatomy  drawn 
up  by  Mundinus,  in  the  year  1315.  It  was  ex- 
traded  principally  from  what  the  Arabians  had 
preferved  of  Galen’s  doClrine  ; and,  rude  as  it  is, 

in 


INTRODUCTION.  15 

in  that  age,  it  was  judged  to  be  fo  mafterly  a 
performance,  that  it  was  ordered  by  a public 
decree,  that  it  Ihould  be  read  in  all  the  fchools 
of  Italy ; and  it  actually  continued  to  be  almoft 
the  only  book  which  was  read  upon  the  fubjedt 
for  above  200  years.  Cortefius  gives  him  the 
credit  of  being  the  great  reftorer  of  anatomy, 
and  the  firft  who  diffecled  human  bodies  among 
the  moderns. 

A general  prejudice  againft  difledtion,  howe- 
ver, prevailed  till  the  i6th  century.  The  em- 
peror Charles  V.  ordered  a confultation  to  be 
held  by  the  divines  of  Salamanca,  in  order  to 
determine  whether  or  not  it  was  lawful  in  point 
of  confcience  to  diffedt  a dead  body.  In  Muf- 
covy,  till  very  lately,  both  anatomy  and  the  ufe 
of  fkeletons  were  forbidden,  the  firft  as  inhu- 
man, and  the  latter  as  fubfervient  to  with- 
craft. 

In  the  beginning  of  the  15th  century,  learn- 
ing revived  confiderably  in  Europe,  and  parti- 
cularly phyfic,  by  means  of  copies  of  the  Greek 
authors  brought  from  the  fack  of  Conftantinople; 
after  which  the  number  of  anatomifts  and  ana- 
tomical books  increafed  to  a prodigious  degree. 
— The  Europeans  becoming  thus  pofteffed  of 
the  antient  Greek  fathers  of  medicine,  were  for 
a long  time  fo  much  occupied  in  corredling  the 
copies  they  could  obtain,  ftudying  the  meaning, 
and  commenting  upon  them,  that  they  at- 
tempted 


i6  INTRODUCTION. 

tempted  nothing  of  their  own,  efpecially  in  ana- 
tomy. 

And  here  the  late  Dr.  Hunter  introduces  in- 
to the  annals  of  this  art,  a genius  of  the  firft 
rate,  Leonardo  da  Vinci, who  had  been  formerly 
overlooked,  becaufe  he  was  of  another  profeffion, 
and  becaufe  he  publifhed  nothing  upon  the  fub- 
jedl.  He  is  confidered  by  the  Doctor  as  by  far 
the  beft  anatomift  and  phyfiologift  of  his  time  ; 
and  was  certainly  the  firft  man  we  know  of  who 
introduced  the  pradice  of  making  anatomical 
drawings. 

Vaflare,  in  his  lives  of  the  painters,  fpeaks  of 
Leonardo  thus,  after  telling  us  that  he  had  com- 
pofed  a book  of  the  anatomy  of  a horfe,  for 
his  own  ftudy  : “ He  afterwards  applied  him- 
felf  with  more  diligence  to  the  human  anatomy; 
in  which  ftudy  he  reciprocally  received  and 
communicated  affiftance  to  Marc  Antonio  della 
Torre,  an  excellent  philofopher,  who  then  read 
ledures  in  Pavia,  and  wrote  upon  this  fubjed  ; 
and  who  was  the  firft,  as  I have  heard,  who 
began  to  illiiftrate  medicine  from  the  dodrine 
of  Galen,  and  to  give  true  light  to  anatomy, 
which  till  that  time  had  been  involved  in  clouds 
of  darknefs  and  ignorance.  In  this  he  availed 
himfelf  exceedingly  of  the  genius  and  labour  of 
Leonardo,  who  made  a book  of  ftudies,  drawn 
with  red  chalk,  and  touched  with  a pen,  with 
great  diligence,  of  fuch  fubjeds  as  he  had  him- 
felf difieded  ; where  he  made  all  the  bones,  and 
3 to 


INTRODUCTION.  17 

to  thofe  he  joined,  in  their  order,  all  the  nerves, 
and  covered  them  with  the  mufcles.  And  con- 
cerning thofe,  from  part  to  part,  he  wrote  re- 
marks in  letters  of  an  ugly  form,  which  are 
written  by  the  left  hand,  backwards,  and  not 
to  be  underftood  but  by  thofe  who  >know  the 
method  of  reading  them ; for  they  are  not  to 
be  read  without  a looking-glafs.  Of  thefe  pa- 
pers of  the  human  anatomy,  there  is  a great 
part  in  the  poifeffion  of  M.  Francefco  daMelzo, 
a Milanefe  gentleman,  who,  in  the  time  of  Leo- 
nardo, was  a mofl;  beautiful  boy,  and  much  be- 
loved by  him,  as  he  is  now  a beautiful  and  gen- 
teel old  man,  who  reads  thofe  writings,  and  care- 
fully preferves  them,  as  precious  relid-s,  toge- 
ther with  the  portrait  of  Leonardo,  of  happy 
memory.  It  appears  impoffible  that  that  divine 
fpirit  fhould  reafon  fo  well  upon  the  arteries, 
and  mufcles,  and  nerves,  and  veins  ; and  with 
fuch  diligence  of  every  thing,  &c.  &c.” 

Thofe  very  drawings  and  the  writings  are 
happily  found  to  be  preferved  in  his  Britannic 
Majefty’s  great  colledtion  of  original  drawings, 
where  the  Dodior  was  permitted  to  examine 
them  ; and  his  fentiments  upon  the  occafion  he 
thus  exprelTes : “ I expeded  to  fee  little  more 
than  fuch  defigns  in  anatomy,  as  might  be  ufe- 
ful  to  a painter  in  his  own  profeffion  ; but  I faw, 
and  indeed  with  aftonifhment,  that  Leonardo 
had  been  a general  and  a deep  ftudent.  When 
I confider  what  pains  he  has  taken  upon  every 

B part 


i8  INTRODUCTION, 

part  of  the  body,  the  fuperiority  of  his  univer- 
fal  genius,  his  particular  excellence  in  mecha- 
nics and  hydraulics,  and  the  attention  with  which 
fuch  a man  would  examine  and  fee  objects  which 
he  was  to  draw,  I am  fully  perfuaded  that  Leo- 
nardo was  the  heft  anatomift  at  that  time  in  the 
world.  We  muft  give  the  1 5th  century  the  cre- 
dit of  Leonardo’s  anatomical  ftudies,  as  he  was 
55  years  of  age  at  the  clofe  of  that  century.” 

In  the  beginning  of  the  1 6th  century,  Achil- 
linus  and  Benedidfus,  but  particularly  Beren- 
garius  and  Maffa,  followed  out  the  improvement 
of  anatomy  in  Italy,  where  they  taught  it,  and 
publifhed  upon  the  fubjedt.  Thefe  firft  im- 
provers made  fome  difcoveries  from  their  own 
diffedbions  ; but  it  is  not  furprifing  that  they 
ihould  have  been  diffident  of  themfelves,  and 
I lave  follovred  Galen  almoft  blindly,  when  his 
authority  had  been  fo  long  eftabliffied,  and  when 
the  enthufiafm  for  Greek  authors  was  rifmg  to 
fuch  a pitch. 

Soon  after  this,  we  may  fay  about  the  year 
1540,  the  great  Vefalius  appeared.  He  was 
Itudious,  laborious,  a.nd  ambitious.  From  Bruf- 
fels,  the  place  of  his  birth,  he  went  to  Louvain, 
and  thence  to  Paris,  where  anatomy  was  riot 
yet  making  confiderable  figure,  and  then  to 
Louvain  to  teach  ; from  which  place,  very  for- 
tunately for  his  reputation,  he  was  called  to  Italy, 
vrhere  he  met  with  every  opportunity  that  fuch 
a fuch  genius  for  anatomy  defire,  that  is,  books, 

fubjedts. 


INTRODUCTION.  19 

fubje(?LS,  and  excellent  draughtlinen.  He  was 
equally  laborious  in  reading  the  ancients,  and  in 
dilTedting  bodies.  And  in  making  the  compa- 
rifon,  he  could  not  but  fee,  that  there  was  great 
room  for  improvement,  and  that  many  of  Ga- 
len’s defcriptions  were  erroneous.  When  he 
was  but  a young  man,  he  publifhed  a noble  fyf- 
tem  of  anatomy,  illuftrated  with  a great  num- 
ber of  elegant  figures. — In  this  work  he  found 
fo  many  occaficns  of  correcting  Galen,  that  his 
contemporaries,  partial  to  antiquity,  and  jealous 
of  his  reputation,  complained  that  he  carried  his 
turn  for  improvement  and  criticifms  to  licentiouf- 
nefs.  The  fpirit  of  oppofition  and  emulation  was 
prefently  roufed  ; and  Silvius  in  France,  Colum- 
bus, Fallopius,  and  Euftachius  in  Italy,  who 
were  all  in  high  anatomical  reputation  about  the 
middle  of  the  1 6th  century,  endeavoured  to  de- 
fend Galen  at  the  expence  of  Vefalius.  In 
their  difputes  they  made  their  appeals  to  the  hu- 
man body : and  thus  in  a few  years  the  art  w'as 
greatly  improved.  And  Vefalius  being  deted;- 
ed  in  the  very  fault  which  he  condemned  in  Ga- 
len,  to  wit,  defcribing  from  the  difl'eCiions  of 
brutes,  and  not  of  the  human  body,  it  expofed 
fo  fully  that  blunder  of  the  older  anatomifts,  that 
in  fucceeding  times  there  has  been  little  reafon 
for  fuch  complaint. — Befides  the  above,  he  pub- 
lifhed feveral  other  anatomical  treatifes.  He 
has  been  particularly  fervdceable  by  impofmg 
names  on  the  mufcles,  moft  of  which  are  retain- 

B 2 ed 


20  INTRODUCTION, 
cd  to  this  day.  Formerly  they  were  diftinguifh- 
ed  by  numbers,  which  were  differently  applied 
by  almoft  every  author. 

In  1561,  Gabriel  Fallopius,  profeflbr  of  ana- 
tomy at  Padua,  publifhed  a treatife  of  anatomy 
under  the  title  of  Obfervatio?ies  Anatomicce.  This 
was  defigned  as  a fupplement  to  Vefalius  ; many 
of  whofe  defcriptions  he  corrects,  though  he 
always  makes  mention  of  him  in  an  honourable 
manner.  Fallopius  made  many  great  difcoveries, 
and  his  book  is  well  worth  the  perufal  of  every 
anatomift. 

In  1563,  Bartholomseus  Euftachius  publifh- 
ed his  Opujcula  Anatomlca  at  Venice,  which 
have  ever  fince  been  juftly  admired  for  the  ex- 
adlnefs  of  the  defcriptions,  and  the  difcoveries- 
contained  in  them.  He  publifhed  afterwards 
forne  other  pieces,  in  which  there  is  little  of  ana- 
tomy ; but  never  publifhed  the  great  work  he 
had  promifed,  which  was  to  be  adorned  with 
copperplates  reprefenting  all  the  parts  of  the 
human  body.  Thefe  plates,  after  lying  buried 
in  an  old  cabinet  for  upwards  of  150  years,  were 
at  laft  difcovered  and  publifhed  in  the  year  1714, 
by  Lancifi  the  pope’s  phyfician ; who  added  a 
fhort  explicatory  text,  becaufe  Euftachius’s  own 
writing  could  not  be  found. 

From  this  time  the  ftudy  of  anatomy  gradu- 
ally diffuled  itfelf  over  Europe  ; infomuch  that 
for  the  laft  hundred  years  it  has  been  daily  im- 
proving by  the  labour  of  a number  of  pro- 

feffed 


INTRODUCTION.  21 

•feffed  anatomifts  almoft  in  every  country  of  Eu- 
rope. 

We  may  form  a judgment  about  the  ftate  of 
anatomy  even  in  Italy,  in  the  beginning  of  the 
I yth  century,  from  the  information  of  Cortefius. 
He  had  been  profeffbr  of  anatomy  at  Bologna, 
and  was  then  profelTor  of  medicine  at  Maflana  ; 
where,  though  he  had  a great  defire  to  improve 
himfelf  in  the  art,  and  to  finifh  a treatife  which 
he  had  begun  on  practical  anatomy,  in  24  years 
he  could  twice  only  procure  an  opportunity  of 
diflediing  a human  body,  and  then  it  was  with 
difficulties  and  in  hurry  ; whereas  he  had  ex- 
pected to  have  done  fo,  he  fays,  onct  eve?y  year, 
according  to  the  ciijiom  in  the  famous  academies  of 
Italy. 

In  the  very  end  of  the  1 6th  centry,  the  great 
Harvey,  as  was  the  cuftom  of  the  times,  went 
to  Italy  to  ftudy  medicine  ; for  Italy  was  ftill  the 
favourite  feat  of  the  arts  : And  in  the  very  be- 
ginning of  the  I yth  century,  foon  after  Har- 
vey’s return  to  England,  his  mafter  in  anatomy, 
Fabricius  ab  Aquapendente,  publiffied  an  ac- 
count of  the  valves  in  the  veins,  which  he  had 
difcovered  many  years  before,  and  no  doubt 
taught  in  his  ledures  when  Harvey  attended  him. 

This  difcovery  evidently  affeded  the  eftabliffi- 
ed  dodrine  of  all  ages,  that  the  veias  carried 
the  blood  from  the  liver  to  all  parts  of  the  body 
for  nouriffiment.  It  fet  Harvey  to  work  upon 
the  ufe  of  the  heart  and  vafcular  fyftems  in  ani- 
mals ; 


22 


INTRODUCTION, 
mals  ; and  in  the  courfe  of  fome  years  he  was 
fo  happy  as  to  difcover,  and  to  prove  beyond  all 
poflibility  of  doubt,  the  circulation  of  tl^e  blood. 
He  taught  his  new  dodlrine  in  his  le^ures  about 
the  year  i6i6,  and  printed  it  in  1628. 

It  was  by  far  the  moll  important  Hep  that  had 
been  made  in  the  knowledge  of  animal  bodies 
in  any  age.  It  not  only  refledled  ufeful  lights 
upon  what  had  been  already  found  out  in  ana- 
tomy, but  alfo  pointed  out  the  means  of  further 
inveftigation.  And  accordingly  we  fee,  that 
from  Harvey  to  the  prefent  time,  anatomy  has 
been  fo  much  improved,  that  we  may  realbna- 
bly  quellion  if  the  ancients  have  been  further 
outdone  by  the  moderns  in  any  other  branch  of 
knowledge.  From  one  day  to  another  there  has 
been  a conftant  fucceffion  of  difcoveries,  relating 
either  to  the  ftrudlure  or  fundlions  of  our  body ; 
and  new  anatomical  procelTes,  both  of  inveftiga- 
tion and  demonftration,  have  been  daily  invent- 
ed. Many  parts  of  the  body,  which  were  not 
known  in  Harvey’s  time,  have  hnce  then  been 
brought  to  light : and  of  thofe  which  were 
known,  the  internal  compofition  and  fun£tions 
remained  unexplained  ; and  indeed  muft  have 
remained  unexplicable  without  the  knowledge 
of  the  circulation. 

Harvqy’s  dodrine  at  firft  met  with  confider- 
able  oppofttion  ; but  in  the  fpace  of  about  20 
years  it  was  fo  generally  and  fo  warmly  embrac- 
ed, that  it  was  imagined  every  thing  in  phyfic 
would  be  explained.  But  time  and  experience 

have 


INTRODUCTION.  23 
have  taught  us,  that  we  ftill  are,  and  probably 
mufl  long  continue  to  be,  very  ignorant ; and 
that  in  the  ftudy  of  the  human  body,  and  of  its 
difeafes,  there  will  always  be  an  extenfive  field 
for  the  exercife  of  fagacity. 

After  the  difcovery  and  knowledge  of  the 
circulation  of  the  blood,  the  next  queftion  would 
naturally  have  been  about  the  paflage  and  route 
of  nutritious  part  of  the  food  or  chyle  from  the 
bowels  to  the  blood-veflels  : And,  by  good  for- 
tune, in  a few  years  after  Harvey  had  made  his 
difcovery,  Afellius,  an  Italian  phyfician,  found 
out  the  la<fi;eals,  or  velTels  which  carry  the  chyle 
from  the  inteftines ; and  printed  his  account  of 
them,  with  coloured  prints,  in  the  year  1627, 
the  very  year  before  Harvey’s  book  came  out. 

For  a number  of  years  after  thefe  two  publi- 
cations, the  anatomifts  in  all  parts  of  Europe 
were  daily  opening  living  dogs,  either  to  fee  the 
lafteals  or  to  obferve  the  phenomena  of  the  cir- 
culation. In  making  an  experiment  of  this 
kind,  Pecquet  in  France  Vv^as  fortunate  enough 
to  difcover  the  thoracic  dud;,  or  common  trunk 
of  all  the  ladeals,  which  conveys  the  chyle  into 
the  fubclavian  vein.  He  printed  his  difcovery  in 
the  year  1651.  And  now  the  ladeals  having;  been 
traced  from  the  inteftines  to  the  thoracic  duct, 
and  that  dud  having  been  traced  to  its  termina- 
tion in  a blood-veftel,  the  paflage  of  the  chyle 
was  completely  made  out. 

The  fame  pradice  of  opening  living  animals 

furnifli- 


24  INTRODUCTION, 
furniflied  occafions  of  difcovering  the  lymphatic 
veffels.  This  good  fortune  fell  to  the  lot  of 
Rudbec  firft,  a young  Swedifh  anatomift ; and 
then  to  Thomas  Bartholine,  a Danifh  anato- 
mifl,  who  was  the  firfl;  who  appeared  in  print 
upon  the  lymphatics.  His  book  came  out 
in  the  year  1653,  years  after  that  of 

Pecquet.  And  then  it  was  very  evident  that 
they  had  been  feen  before  by  Dr.  Higmore  and 
others,  who  had  miftaken  them  for  ladeais.  But 
none  of  the  anatomifts  of  thofe  times  could  make 
out  the  origin  of  the  lymphatics,  and  none  o^ 
of  the  phyfiologifts  could  give  a fatisfaftory  ac- 
Cou*nt  of  their  ufe,  , ; 

The  circulation  of  the  blood  and  the  palTage 
of  the  chyle  having  been  fatisfa<ftorily  traced  out 
in  full  grown  animals,  the  anatomifts  were  na- 
turally led  next  to  confider  how  thefe  animal 
procefies  w^ere  carried  on  in  the  child  while  in 
the  womb  of  the  mother.  Accordingly  the 
male  and  female  organs,  the  appearances  and 
contents  of  the  pregnant  uterus,  the  incubated 
egg,  and  every  phenomenon  wdiich  could  illuf- 
trate  generation,  became  the  favourite  fubjeft, 
for  about  30  years,  with  the  principal  anatomifts 
of  Europe. 

Thus  it  would  appear  to  have  been  in  theory: 
but  Dr.  Hunter  believes,  that  in  fad;,  as  Har- 
vey’s mafcer  Fabricius  laid  the  foundation  for 
the  difcovery  of  the  circulation  of  the  blood  by 
teaching  him  the  valves  of  the  veins,  and  there- 
by 


INTRODUCTION.  25 

by  inviting  him  to  confider  that  fubjedt ; fo  Fa- 
bricius  by  his  lectures,  and  by  his  elegant  work 
De  formato  fcetu^  et  de  formatione  ovi  et  pulli^ 
probably  made  that  likewife  a favourite  fubjedt 
with  Dr.  Harvey.  But  whether  he  took  up 
the  fubjedt  of  generation  in  confequence  of  his 
difcovery  of  the  circulation,  or  was  led  to  it  by 
his  honoured  mafter  Fabricius,  he  fpent  a great 
deal  of  his  time  in  the  enquiry  ; and  publilTied 
his  obfervations  in  a book  De generatione  anama-^ 
lium^  in  the  year  1 65 1 , that  is  fix  years  before 
his  death. 

In  a few  years  after  this,  Sv'ammerdam,  Van 
Horn,  Steno,  and  De  Graaf,  excited  great  atten- 
tion to  the  fubjedt  of  generation,  by  their  fup- 
pofed  difcovery  that  the  females  of  vivaparous 
animals  have  ovaria,  that  is,  clufters  of  eggs  in 
their  loins,  like  oviparous  animals  ; which  when 
impregnated  by  the  male,  are  conveyed  into  the 
uterus  : fo  that  a child  is  produced  from  an  egg 
as  well  as  a chick  ; with  this  difference,  that  one 
is  hatched  within,  and  the  other  without,  the 
body  of  the  mother. 

Malpighi,  a great  Italian  genius,  fome  time 
after,  made  confiderable  advances  upon  the  fub- 
jedl  of  generation.  He  had  the  good  fortune 
to  be  the  lirft  who  ufed  magnifying  glaffes  with 
addrefs  in  tracing  the  firft  appearances  in  the  for- 
mation of  animals.  He  likewife  made  many 
other  obfervations  and  improvements  in  the  mi- 

nutiae 


26  INTRODUCTION. 

of  anatomy  by  his  mifcrofcopical  labours, 
and  by  cultivating  comparative  anatomy. 

This  diftinguilhed  anatomift  gave  the  firft 
public  fpecimen  of  his  abilities,  by  printing  a dif- 
fertation  on  the  lungs  a?mo  i66i  ; a period  fo 
remarkable  for  the  ftudy  of  nature,  that  it 
would  be  injuftice  to  pafs  it  without  particular 
notice. 

At  the  fame  time  flourifhed  Laurentius  Belli- 
nus  at  Florence,  and  was  the  firft  who  intro- 
duced mathematical  reafoning  in  phyfic.  In 
1662,  Simon  Pauli  publiftied  a treatife  Dc  Al- 
bandis  ojjibus.  He  had  long  been  admired  for  the 
white  fkeletons  he  prepared ; and  at  laft  difcove- 
red  his  method,  which  was  by  expofing  the  bones 
all  winter  to  the  weather. 

Johannes  Swammerdam  of  Amfterdam  alfo 
publifhed  fome  anatomical  treatifes ; but  was 
moft  remarkable  for  his  knowledge  of  preferv- 
ing  the  parts  of  bodies  entire  for  many  years, 
by  injedting  their  vefTels.  He  alfo  publiftied  a 
treatife  on  infpiration  ; wherein  he  mentioned 
his  having  figures  of  all  the  parts  of  the  body 
at  big  as  the  life,  cut  in  copper,  which  he  de- 
figned  to  publifli,  with  a complete  fyftem  of 
anatomy.  Thefe,  however,  were  never  made 
public  by  Swammerdam;  but,  in  1683,  Go- 
thofridus  Bidloo,  profeftbr  of  anactomy  at  Ley- 
den, publifhed  a work  intitled  Anatomla  corporis 
humani^  where  all  the  parts  were  delineated  in 
very  large  plates  as  alm.oft  as  big  as  the  life.  Mr. 

Cow'^per, 


INTRODUCTION.  27 

Cowper,  an  Englifli  furgeon,  bought  300  co- 
pies of  thefe  figures  ; and  in  1698,  publifhed 
them  witli  an  Englifh  text,  quite  different  from 
Bidioo’sLatin  one;  to  which  were  added  letters  in 
Bidloo’s  figures,  and  fome  few  figures,  of  Mr. 
Cowper’s  own.  To  this  w^ork  Cowper’s  name 
was  prefixed,  without  the  leafl  mention  of  Bid- 
loo,  except  on  purpofe  to  confute  him.  Bid- 
loo  immediately  publifhed  a ver)'  ill-natured 
pamphlet,  called  Gulidmus  Co’wperus  citatiis  coram 
tribimali ; appealing  to  the  Royal  Society,  how 
far  Cowper  ought  to  be  punifhed  as  a plagiary 
of  the  wcrit  kind,  and  endeaYCuring  to  prove 
him  an  ignorant  deceitful  fellow.  Cowper  an- 
fwered  him  in  his  own  flyle,  in  a pamphlet  call- 
ed his  Vindlcics  ; endeavouring  to  prove,  either 
that  Bidloo  did  not  underftand  his  own  ta- 
bles, or  that  they  were  none  of  his.  It  was 
even  alledged  that  thofe  w^ere  the  tables  promif- 
ed  by  Swammerdam,  and  which  Bidloo  had 
got  from  his  widow.  This,  however,  appears 
to  have  been  only  an  invidious  furmife,  there 
being  unqueftionable  evidence  that  they  were 
really  the  performance  of  Bidloo. 

Soon  after,  Ifbrandus  Diembroeck,  profelfor 
of  anatomy  at  Utrecht,  began  to  appear  as 
an  author.  His  work  contained  very  little  ori- 
ginal ; but  he  was  at  great  pains  to  coll  eel  from 
others  what  was  valuable  in  their  veritings,  and 
his  fyftem  was  the  common  ftandard  among  ana- 
tomical feudents  for  many  years. 

About  the  fame  time,  Antonius  Liewmn- 

hoeck 


28  INTRODUCTION, 
hoeck  of  Delft,  improved  confiderably  on  Mal- 
pighi’s ufe  of  microfcopes.  Thefe  two  authors 
took  up  anatomy  where'  others  had  dropt  it ; 
and,  by  this  new  art,  they  brought  a number 
of  amazing  things  to  light.  They  difcovered 
the  red  globules  of  the  blood ; they  were  ena- 
bled to  fee  the  adtual  circulation  of  the  blood  in 
the  tranfparent  parts  of  living  animals,  and  could 
meafure  the  velocity  of  its  motion;  they  difco- 
vered that  the  arteries  and  veins  had  no  interme- 
diate cells  or  fpungy  fubftance,  as  Harvey  and 
all  the  preceding  anatomifts  had  fuppofed,  but 
communicated  one  with  the  other  by  a continu- 
ation of  the  fame  tube. 

Liewenhoeck  was  in  great  fam.e  likewife  for 
his  difcovery  of  the  animalcula  in  the  femen. 
Indeed  there  was  fcarcely  a part  of  the  body, 
folid  or  fluid,  which  efcaped  his  examination  ; 
and  he  almoft  every  where  found,  that  what 
appeared  to  the  naked  eye  to  be  rude  undigeft- 
ed  matter,  was  in  reality  a beautiful  and  regular 
compound. 

After  this  period,  Nuck  added  to  our  know- 
ledge of  the  abforbent  fyftem  already  mentioned, 
by  his  injeftions  of  the  lymphatic  glands;  Ruyfch,- 
by  his  defcription  of  the  valves  of  the  lymphatic 
veffels ; and  Dr.  Meckel,  by  his  accurate  ac- 
count of  the  whole  fyftem,  and  by  tracing  thofe 
velTels  in  many  parts  where  they  had  not  before 
been  defcribed. 

Befides  thefe  authors,  Drs.  Hunter  and  Monro 

have 


INTRODUCTION.  29 

have  called  the  attention  of  the  public  to  this 
part  of  anatomy,  in  their  controverfy  concern- 
ing the  difcovery  of  the  office  of  the  lympha-  ' 
tics. 

When  the  lymphatic  veffels  were  hrft  feen  and 
traced  into  the  thoracic  dudt,  it  was  natural  for 
anatomifcs  to  fufpedt,  that  as  the  ladeals  abforb- 
ed  from  the  cavity  of  the  inteftines,  the  lym- 
phatics, which  are  fimilar  in  figure  and  fcruc- 
ture,  might  poffibly  do  the  fame  office  with 
refped;  to  other  parts  of  the  body : and  accord- 
ingly, Dr.  Gliffon,  who  wrote  in  1654,  fup- 
pofes  thefe  veffels  arofe  from  cavities,  and  that 
their  ufe  was  to  abforb  ; and  Frederic  Floffman 
has  very  explicitly  laid  down  the  dodtrine  of  the 
lymphatic  veffels  being  a fyftem  of  abforbents. 
But  anatomifts  in  general  have  been  of  a con- 
trary opinion ; for,  from  experiments,  particu- 
larly fuch  as  were  made  by  injedtions,  they  have 
been  perfuaded  that  the  lymphatic  veffels  did  not 
arife  from  cavities,  and  did  not  abforb,  but  were 
merely  continuations  from  finall  arteries.  The 
dodtrine,  therefore,  that  the  lymphatics,  like 
the  ladteals,  were  abforbents,  as  had  been  fug- 
gefted  by  Gliffon  and  by  Hoffman,  has  been 
revived  by  Dr.  Hunter  and  Dr.  Monro,  who 
have  controverted  the  experiments  of  their  pre- 
deceffbrs  in  anatomy,  and  have  endeavoured  to 
prove  that  the  lymphatic  veffels  are  not  continu- 
ed from  arteries,  but  are  abforbents. 

To  this  dodlrine,  however,  fevera)  objedions 

have 


30  INTRODUCTION, 
have  been  ftarted,  particularly  by  Haller  (Elm. 
Phyf.  1.  24. § 2,  3.) ; and  it  has  been  found,  that 
before  thedo£trine  of  thelymphaticsbeingafyftem 
of  abforbents  can  be  eftablifhed,  it  muft  firft  be 
determined  w^hether  this  fyftem  is  to  be  found  in 
other  animals  belides  man  and  quadrupeds.  Mr. 
Hewfon  claims  the  merit  of  having  proved  the 
afnrmative  of  this  queftion,  by  difcovering  the 
lymphatic  fyftem  in  birds,  ftih,  and  amphibious 
animals.  See  Fhil.  'Tranf.  vol.  Iviii.  and  Ixix. 
— And  latterly,  Mr.  Cruikfhank  has  traced  the 
ramifications  of  that  fyftem  in  almoft  every  part 
of  the  body  ; and  from  his  diftefiions,  figures 
have  been  made  and  lately  publifhed  to  the 
v/orld.  To  Mr.  Seldon  alfo  we  are  much  in- 
debted for  his  illuftration  of  this  fyftem,  which 
promifes  to  give  great  fatisfacftion,  but  of  which 
only  a part  has  yet  been  publifhed. 

The  gravid  uterus  is  a fubjedt  likewife  which 
has  received  confiderable  improvements,  parti- 
cularly relating  to  one  very  important  difcovery  ; 
viz.  that  the  internal  membrane  of  the  uterus, 
which  Dr.  Hunter  has  named  decidua^  confti- 
tutes  the  exterior  part  of  the  fecundines  or  after- 
birth, and  feparates  from  the  reft  of  the  uterus 
every  time  that  a woman  either  bears  a child  or 
fuffers  a mifcarriage.  This  difcovery  includes 
another,  to  vrit,  that  the  placenta  is  partly  made 
up  of  an  excrefcence  or  efflorefcence  from  the 
uterus  itfelf, 

Thefe  difcoveries  are  of  the  utmoft  confe- 
3 quence. 


INTRODUCTION.  31 

quence,  both  in  the  phyfiological  queftion  about 
the  connection  betvveen  the  mother  and  child, 
and  likewife  in  explaining  the  phenomena  of 
births  and  abortions,  as  well  as  in  regulating  ob- 
ftetrical  praCtice. 

The  anatomifts  of  this  century  have  improv- 
ed anatomy,  and  have  made  the  ftudy  of  it  luuch 
more  eafy  by  giving  us  more  correCt  as  well  as 
more  numerous  figures.  It  is  amazing  to  think 
of  what  has  been  done  in  that  time.  We  have 
had  four  large  folio  books  of  figures  of  the 
bones,  viz.  Chefelden’s,  Albinus’s,  Sue’s  and 
Trew’s.  Of  the  mufcles,  we  have  had  two  large 
folio’s ; one  from  Cowper,  which  is  elegant ; 
and  one  from  Albinus,  which  from  the  accuracy 
and  labour  of  the  work,  we  may  fuppofe  will 
never  be  outdone.  Of  the  blood  veffels  we 
have  a large  folio  from  Dr.  Haller.  We  have 
had  one  upon  the  nerves  from  Dr.  Meckel,  and 
another  by  Dr.  Monro,  junior.  We  have  had 
Albinus’s,  Roederer’s,  Jenty’s,  and  Hunter’s 
works  upon  the  pregnant  uterus ; Weitbrecht 
and  Leber  on  the  joints  and  frefh  bones  ; Soe- 
merring  on  the  brain  ; Zin  on  the  eye  ; Cotun- 
nius,  Mekel,  junior,  &c.  on  the  ear  ; Walterus 
on  the  nerves  of  the  thorax  and  abdomen  ; Dr. 
Monro  on  the  buiTse  mucofae,  &c. 

It  would  be  endlefs  to  mention  the  ana.tomical 
figures  that  have  been  publifhed  in  this  centuiy, 
of  particular  and  fmaller  parts  of  the  body,  by 
Morgagni,  Ruyfch,  Valfalva,  SanCcorini,  Hei- 


32  INTRODUCTION. 

fter,  Vater,  Cant,  Zimmerman,  Waltems,  and 

others. 

Thofe  elegant  plates  of  the  brain,  however, 
juft  publilhed  by  M.  Vicq.  d’Azyr,  muft  not 
pafs  without  notice,  efpecially  as  they  form  part 
of  an  univerfal  fyftem  of  anatomy  and  phyfi- 
ology,  both  human  and  comparative,  propofed 
to  be  executed  in  the  fame  fplendid  ftyle.  Up- 
on the  brain  alone  1 9 folio  plates  are  employed  j 
of  which  feveral  are  coloured.  The  figures  are 
delineated  with  accuracy  and  clearnefs  ; but  the 
colouring  is  rather  beautiful  than  correct.  Such 
parts  of  this  work  as  may  be  publifhed,  cannot 
fail  to  be  equally  acceptable  to  the  anatomift  and 
the  philofopher  ; but  the  entire  defign  is  appa- 
rently too  extenfive  to  be  accomplifhed  within 
the  period  of  a fingle  life.  In  Great  Britain, 
alfo,  a very  great  anatomical  work  is  carrying 
on  by  Andrew  Bell,  F.S.A.S.  engraver  to  his 
Royal  Highnefs  the  Prince  of  Wales,  with  the 
approbation  of  Dr.  Monro,  and  under  the  in- 
fpeTion  of  his  very  ingenious  affiftant  Mr.  Fyfe. 
It  is  to  compofe  a complete  illuftration,  both  ge- 
neral and  particular,  of  the  human  body,  by  a 
felecftion  from  the  beft  plates  of  all  the  greateft 
anatomifts,  as  well  foreign  as  Britifh,  exhibit- 
ing the  lateft  cliicoveries  in  the  fcience,  and  ac- 
companied with  copious  explanations.  The 
whole  number  of  plates  mentioned  in  the  Pro- 
fpecftus  is  240,  of  which  152  are  already  done  ; 
all  in  royal  folio. 


To 


, INTRODUCTION.  33 

To  the  foreign  treat ifes  already  mentioned  may 
be  added  thofe  recently  publiflied  by  babbatier 
and  Plenck  on  anatomy  in  general.  In  Great- 
Britain,  the  writings  of  Keil,  Douglas,  Chefel- 
den,  the  firft  M onro,  Winflow,  &c.  are  too  well 
known  to  need  defcription.  The  laft  of  thefe 
ufed  to  be  recommended  as  a ftandard  for  the  ltu« 
dents  of  anatomy  : but  it  has  of  late  given  place 
to  a more  accurate  and  comprehenfive  fyilem, 
in  three  volumes,  publifhed  by  Mr  Elliot  of 
Edinburgh,  upon  a plan  approved  of  by  Dr  Mon- 
ro, and  executed  by  Mr  Fyfe.  Dr  Simmons 
of  I.ondon  has  alfo  obliged  the  world  with  an 
excellent  fyftem  of  anatomy  ; and  another  work, 
under  the  title  of  “ Elements  of  Anatomy  and 
the  Animal  QHconomy  : in  which  the  fubjedts 
are  treated  with  uncommon  elegance  and  perfpi- 
cuity. 

In  the  latter  part  of  the  laft  century,  anatomy 
made  two  great  fteps,  by  the  invention  of  injec- 
tions, and  the  method  of  making  what  we  com- 
monly call  preparations.  Thefe  two  modern  arts 
have  really  been  of  infinite  ufe  to  anatomy  ; and 
befides  have  introduced  an  elegance  into  our  ad- 
miniftrations,  which  in  former  times  could  not 
have  been  fuppofed  to  be  polfible.  They  arofe 
in  Holland  under  Swammerdam  and  Ruyfch, 
and  afterwards  in  England  under  Cowper,  St. 
Andre,  and  others,  where  they  have  been  greatly 
improved. 


C 


The 


34  INTRODUCTION. 

The  anatom ifts  of  former  ages  had  no  other 
knov/ledge  of  the  blood-veffels,  than  what  they 
were  able  to  collect  from  laborious  dilfedtions, 
and  from  examining  the  fmaller  branches  of  them, 
upon  fome  lucky  occafion,  when  they  were  found 
more  than  commonly  loaded  with  red  blood. 
But  filling  the  vafcular  fyftem  with  a bright  co- 
loured wax,  enables  us  to  trace  the  large  velfels 
with  great  eafe,  renders  the  fmaller  much  more 
confpicuous,  and  makes  thoufands  of  the  very 
minute  ones  vifible,  which  from  their  delicacy, 
and  the  tranfparency  of  their  natural  contents, 
are  otherwife  imperceptible. 

The  mmdern  art  of  corroding  the  flelhy  parts 
with  a menftruum,  and  of  leaving  the  moulded 
wax  entire,  is  fo  exceedingly  ufeful,  and  at  the 
fame  time  fo  ornamental,  that  it  does  great  honour 
tp  the  ingenious  inventor  Dr  Nicholls. 

The  wax-work  art  of  the  moderns  might  de- 
fcrve  notice  in  any  hiftory  of  anatomy,  if  the 
mafters  in  that  way  had  not  been  fo  carelefs  in 
their  imitation.  Many  of  the  wax-figures  are 
fo  tawdry  with  a Iliow  of  unnatural  colours,  and 
fo  very  incorrect  in  the  circumftances  of  figure, 
fituation,  and  the  like,  that  though  they  ftrike 
a vulgar  eye  with  admiration,  they  muft  appear 
ridiculous  to  an  anatomift.  But  thofe  figures 
which  are  caft  in  wax,  plafter,  or  lead,  from  the 
real  fubjedr,  and  which  of  late  years  have  been 
frequently  made,  are,  of  courfe,  very  correct  in 
all  the  principal  parts,  and  may  be  confidered  as 

no 


INTRODUCTION.  35 

no  infignificant  acquifition  to  modern  anatomy. 
The  proper,  or  principal  ufe  of  this  art  is,  to  pre- 
ferve  a very  perfect  likenefs  of  fuch  fubje(3:s  as 
we  but  feidom  can  meet  with,  or  cannot  v/ell 
preferve  in  a natural  ftate  j a fubjed;  in  pregnan- 
cy, for  example. 

The  modern  improved  methods  of  preferving 
animal  bodies,  or  parts  of  them,  has  been  of 
the  greateft  fervice  to  anatomy ; efpecially  in 
faving  the  time  and  labour  of  the  anatomift  in 
the  nicer  diffedions  of  the  fmall  parts  of  the  bo- 
dy. For  now,  whatever  he  has  prepared  with 
care,  he  can  preferve  ; and  the  objed  is  ready  to 
be  feen  at  any  time.  And  in  the  fame  manner 
he  can  preferve  anatomical  curiofities,  or  rarities 
of  every  kind ; fach  as,  parts  that  are  uncom- 
monly formed  ; parts  that  are  difeafed  ; the  parts 
of  the  pregnant  uterus  and  its  contents.  Large 
colledions  of  fuch  curiofities  which  modern 
anatomifts  are  ftriving  almoft  every  where  to 
procure,  are  of  infinite  fervice  to  the  art,  efpe- 
cially in  the  hands  of  teachers.  They  give  Un- 
dents clear  ideas  about  many  things  which  it  is 
very  elTential  to  know,  and  yet  which  it  is  im- 
poffible  that  a teacher  fhould  be  able  to  fhow 
otherwife,  were  he  ever  fo  well  fupplied  with 
frefh  fubjeds. 


36  . INTRODUCTION. 

§ 2.  Vie-w  of  the  Subject  in  general^  and  Plan  of 
the  follo’wing  Preatife. 

The  etymology  of  the  word  anatomy^  as  above 
given,  implies  fimply  dif'eclion  ; but  by  this  term 
lomething  more  is  ufually  underftood. 

It  is  every  day  made  ufe  of  to  exprefs  a know- 
ledge of  the  human  body ; and  a perfon  who 
is  faid  to  underftand  anatomy,  is  fuppofed  to  be 
converfant  with  the  hrufture  and  arrangement  of 
the  different  folid  parts  of  the  body. 

It  is  commonly  divided  into  Anatomy^  pro- 
perly fo  called  ; and  Comparative  Anatomy  ; the 
firft  of  thefe  is  confined  folely  to  the  human  bo- 
dy ; the  latter  includes  all  animals,  fo  far  as  a 
knowledge  of  their  ftruflure  may  tend  to  perfect 
our  ideas  of  the  human  body.  See  Compara- 
tive A'fiatomy. 

The  term  anatomy  may  alfo  have  another  and 
more  extenfive  fignification  : it  may  be  employ- 
ed to  exprefs  not  only  a knowledge  of  the  ftruc- 
ture  and  difpofition  of  the  parts  but  likewife  of 
their  economy  and  ufe.  Confidered  in  this  light, 
it  will  feldom  fail  to  excite  the  curiofity  of  peo- 
ple of  tafce,  as  a branch  of  philofophy  ; fince,  if 
it  is  pleafing  to  be  acquainted  with  the  ftrufture 
of  the  body,  it  is  certainly  more  fo  to  difcover  all 
the  fprings  which  give  life  and  motion  to  the 
machine,  and  to  obferve  the  admirable  mechan- 
ifm  by  which  fo  many  different  functions  are  ex- 
ecuted. 

Aftronomy  and  anatomy,  as  Dr  Hunter,  after 

Fontenelle, 


INTRODUCTION.  37 

Fontenelle,  obferves,  are  the  ftudies  which  pre- 
fent  us  with  the  moft  ftriking  view  of  the  two 
greateft  attributes  of  the  Supreme  Being.  The 
firif  of  thefe  fills  the  mind  with  the  idea  of  his 
immenfity,  in  the  largenefs,  diftances,  and  num- 
ber of  the  heavenly  bodies ; the  laft,  aftoniflies 
with  his  intelligence  and  art  in  the  variety  and 
delicacy  of  animal  mechanifm. 

The  human  body  has  been  commonly  enough 
known  by  the  name  of  microcofmus ^ or  the  little 
world ; as  if  it  did  not  differ  fo  much  from  the 
univerfal  fyftem  of  nature  in  the  fymmetry  and 
number  of  its  parts  as  in  their  fize. 

Galen’s  excellent  treatife  De  ufu  -partium^  was 
compofed  as  a profe  hymn  to  the  Creator ; and 
abounds  with  as  irrefiffible  proofs  of  a fupreme 
Caufe  and  governing  Providence,  as  we  find  in 
modern  phyficotheology.  And  Cicero  dwells  more 
on  the  ftrudfure  and  oeconomy  of  animals  than 
on  all  the  produdfions  of  nature  befides,  when  he 
wants  to  prove  the  exiftence  of  the  gods  from 
the  order  and  beauty  of  the  univerfe.  He  there 
takes  a furvey  of  the  body  of  man  in  a moft  ele- 
gant fynopfis  of  anatomy,  and  concludes  thus  ; 
“ Quibus  rebus  expofitis,  fatis  docuiffe  videor, 
hominis  natura,  quanto  omnes  anteiret  animan- 
tes.  Ex  quo  debet  intelligi,  nee  figuram  fitumque 
rnembrorum,  nec  ingenii  mentifque  vijn  talem 
effici  potuiffe  fortuna.” 

The  fatisfadlion  of  mind  which  arifes  from  the 
ftudy  of  anatomy,  and  the  influence  which  it 

muft 


38  INTRODUCTION, 

mud  naturally  have  upon  our  minds  as  philofo- 
phcrs,  cannot  be  better  conveyed  than  by  the 
following  paflage  from  the  fame  author : “ Quae 
contuens  animus,  accepit  ab  his  cognitionem  de- 
orem,  ex  qua  oritur  pietas  : cui  conjundfa  juffci- 
tia  eft,  reliquaeque  virtutes:  ex  quibus  vita  beata 
exfiftit,  par  et  fimiles  deomm,  nulla  alia  re  nib 
imrnortalitate,  qu^  nihil  ad  bene  vivendum  per- 
tinet,  cedens  coelePcibus.” 

It  would  be  endlefs  to  quote  the  animated 
pafl'ages  of  this  fort  which  are  to  be  found  in  the 
phyficians,  philofophers,  and  theologifts,  who 
have  confidered  the  ftruflure  and  fundlions  of 
animals  with  a viev/  towards  the  Creator.  It  is 
a view  which  muft  ftrike  one  with  a moft  awful 
conviftion.  Who  can  know  and  confider  the 
thoufand  evident  proofs  of  the  alfonifliing  art  of 
the  Creator,  in  forming  and  fuftaining  an  animal 
body  fuch  as  ours,  without  feeling  the  moft  plea- 
fant  enthufiafm?  Can  we  ferioufly  refledt  upon 
this  awful  fabjedf,  without  being  almoft  loft  in 
adoration  ? without  longing  for  another  life 
after  this,  in  v^^hich  we  may  be  gratified  with  the 
higheft  enjoyment,  which  our  faculties  and  na- 
ture feem  capable  of,' the  feeing  and  comprehend- 
ing the  whole  plan  of  the  Creator,  in  forming 
the  iiniverfe  and  in  diredfing  all  its  operations  ? 

But  the  more  immediate  purpofes  of  anatomy 
concern  thofe  who  are  to  be  the  guardians  of 
health,  as  this  ftudy  is  neceffary  to  lay  a foun- 
dation for  all  the  branches  of  medicine.  The 


more 


INTRODUCTION.  39 

more  we  know  of  our  fabric,  the  more  reafon 
we  have  to  believe,  that  if  our  fenfes  vv^ere  more 
acute,  and  our  judgment  more  enlarged,  we 
fhould  be  able  to  trace  many  fprings  of  life  which 
are  now  hidden  from  us  : by  the  fame  fagacity 
we  fhould  difcover  the  true  caufes  and  nature  of 
difeafes ; and  thereby  be  enabled  to  reftore  the 
health  of  many,  who  are  now,  from  our  more 
confined  knowledge,  faid  to  labor  under  incura- 
ble diforders.  By  fuch  an  intimate  acquaintance 
with  the  oeconomy  of  our  bodies,  we  Ihould  dif- 
cover even  the  feeds  of  difeafes,  and  deftroy 
them  before  they  had  taken  root  in  the  conftitu- 
tion. 

That  anatomy  is  the  very  bafis  of  furgery  eve- 
ry body  allows.  It  is  diffedlion  alone  that  can 
teach  us,  where  we  may  cut  the  living  body 
with  freedom  and  difpatch  ; and  where  we  may 
venture  with  great  circumfpedtion  and  delicacy  ; 
and  where  we  muft  not,  upon  any  account,  at- 
tempt it.  This  informs  the  head^  gives  dexterity 
to  the  hand^  and  familiarizes  the  heart  with  a 
fort  of  necelfary  inhumanity,  the  ufe  of  cutting- 
inftruments  upon  our  fellow-creatures. 

Befides  the  knowledge  of  our  body,  through 
all  the  variety  of  its  JlruElure  and  operatmis  in  a 
found  ftate,  it  is  by  anatomy  only  that  we  can  ar- 
rive at  the  knowledge  of  the  true  nature  of  mofi; 
of  the  difeafes  which  afflidt  humanity.  The 
fymptoms  of  many  diforders  are  often  equivo- 
cal j and  difeafes  themifelves  are  thence  frequent- 


40  INTRODUCTION, 

ly  miftaken,  even  by  fenfible,  experienced,  and 
attentive  pliylicians.  But  by  anatomical  exa~ 
mination  after  death,  w^e  can  with  certainty  find 
out  the  miftake,  and  learn  to  avoid  it  in  any  fimi- 
lar  cafe. 

This  ufe  of  anatomy  has  been  fo  generally 
adopted  by  the  moderns,  that  the  cafes  already 
piibliflied  are  a^moft  innumerable;  Mangetus, 
Morgagni,  indeed  many  of  the  beft  modern 
writings  in  phyfic,  are  full  of  them.  And  if 
we  look  among  the  phyficians  of  the  beft  charac- 
ter, and  obferve  thofe  who  have  the  art  itfelf, 
rather  than  the  craft  of  the  profeftion  at  heart ; 
we  (hall  find  them  conftantly  taking  pains  to  pro- 
cure leave  to  examine  the  bodies  of  their  pati- 
ents after  death. 

After  having  confidered  the  rife  and  progrefs 
of  anatomy ; the  various  difcoveries  that  have 
been  made  in  it,  from  time  to  time ; the  great 
number  of  diligent  obfervers  who  have  applied 
themfelvcs  to  this  art ; and  the  importance  of 
the  ftudy,  not  only  for  the  prevention  and  cure 
of  difeafes,  but  in  furnifhing  the  livelieft  proofs 
of  divine  wifdom  ; the  following  queftions  feem 
naturally  to  arife : For  what  purpofe  is  there 
ftich  a variety  of  parts  in  the  human  body  ? Why 
fudi  a complication  of  nice  and  tender  machine- 
ry ? Why  was  there  not  rather  a more  fimple, 
lefs  delicate,  and  lefs  expenfive  frame  (a)  ? 

In 

(a)  The  folloving  beautiful  repreleutation  is  taken  from 
the  late  Dr  Hunter’s  Introduclory  Lecture  in  Anatomy. 


INTRODUCTION.  41 

In  order  to  acquire  a fatisfa£tory  general  idea 
of  this  fubjed:,  and  find  a folution  of  all  fiich 
queftions,  let  us,  in  our  imaginations,  make  a 
man  : in  other  words  let  Us  fuppofe  that  the 
mhid^  or  immaterial  part,  is  to  be  placed  in  a cor- 
poreal fabric,  in  order  to  hold  a correfpondence 
with  other  material  beings  by  the  intervention  of 
the  body  ; and  then  confider,  a priori.^  what  will- 
be  wanted  for  her  accommodation.  In  this  in- 
quiry, we  fhall  plainly  fee  the  neceffity  or  advan- 
tage, and  therefore  the  final  caufe,  of  mofi:  of 
the  parts  which  we  adualiy  find  in  the  human 
body.  And  if  we  confider  that,  in  order  to  an- 
fwer  fome  of  the  requifites,  h aman  wit  and  in- 
vention would  be  very  infufficient  ; we  need  not 
be  furprifed  if  we  meet  with  fome  parts  of  the 
body  whofe  ufe  we  cannot  yet  perceive,  and  with 
fome  operations  and  fundions  which  we  cannot 
explain.  We  can  fee  that  the  whole  bears  the 
moft  ftriking  charaders  of  excelling  wifdom  and 
ingenuity  ; but  the  imperfed  fenfes  and  capacity 
of  man  cannot  pretend  to  reach  ever)^  part  of  a 
machine,  which  nothing  lefs  than  the  intelligence 
and  power  of  the  Supreme  Being  could  contrive 
and  execute. 

Firft,  then,  the  mind^  the  thinking,  immate- 
rial agent,  mu  ft  be  provided  with  a place  of  im- 
mediate refidence,  which  fhall  have  all  the  re- 
quifites for  the  union  of  fpirit  and  body ; ac- 
accordingly  fhe  is  provided  with  the  brain,  where 

fhe 


42  INTRODUCTION. 

fhe  dwells  as  governor  and  fuperintendant  of  the 

whole  fabric. 

In  the  next  place,  as  fhe  is  to  hold  a corref- 
pondence  with  ail  the  material  beings  around  her, 
the  muft  be  fupplied  with  organs  fitted  to  receive 
the  different  kinds  of  impreffions  which  they  will 
make.  In  fadl,  therefore,  we  fee  that  fhe  is  pro- 
vided with  the  organs  of  fenfe,  as  we  call  them  : 
the  eye  is  adapted  to  light ; the  ear  to  found  ; the 
nofe  to  fmell ; the  mouth  to  tafte  ; and  the  fkin 
to  touch. 

Further  : She  muft  be  furnifhed  with  organs 
of  communication  between  herfelf  in  the  brain 
and  thofe  organs  of  fenfe,  to  give  her  informa- 
tion of  all  the  impreffions  that  are  made  upon 
them  : and  fhe  muft  have  organs  between  herfelf 
in  the  brain  and  every  other  part  of  the  body, 
fitted  to  convey  her  commands  and  influence  over 
the  whole.  For  thefe  purpofes  the  nerves  are 
acftually  fgiven.  They  are  chords,  which  rife 
from  the  brain,  the  immediate  refidence  of  the 
mind,  and  difperfe  themfelves  in  branches 
through  all  parts  of  the  body.  They  convey  all 
the  different  kinds  of  fenfations  to  the  mind,  in 
the  brain  ; and  iikewife  carry  out  from  thence 
ail  her  commands  or  influence  to  the  other  parts 
of  the  body.  They  are  intended  to  be  occafion- 
al  monitors  againft  all  fuch  impreffions  as  might 
endanger  the  well-being  of  the  whole,  or  of  any 
particular  pait ; vrhich  vindicates  the  Creator  of 
ail  things,  in  having  adluaily  fubjedted  us  to 


INTRODUCTION.  43 

thofe  many  difagreeable  and  painful  fenfations 
which  we  are  expofed  to  from  a thoufand  acci- 
dents in  life. 

Moreover,  the  mind,  in  this  corporeal  fyftem, 
muft  be  endued  with  the  power  of  moving  from 
place  to  place,  that  £he  may  have  intercourfe 
with  a variety  of  objects  ; that  Ihe  may  Hy  from 
fuch  as  are  difagreeable,  dangerous  or  hurtful, 
and  purfue  fuch  as  are  pleafapt  or  ufeful  to  her. 
And  accordingly  Ihe  is  furniflred  with  limbs,  and 
with  mufcles  and  tendons,  the  inftruments  of  mo- 
tion, which  are  found  in  every  part  of  the  fabric 
where  motion  is  neceffary. 

But  to  fupport,  to  give  nrmnefs  and  fhape  to 
the  fabric  ; to  keep  the  fcfter  parts  in  their  pro- 
per places  ; to  give  fixed  points  for,  and  the  pro- 
per direction  to  its  motions,  as  well  as  to  protedl 
fome  of  the  more  important  and  tender  organs 
from  external  injuries  ; there  muft  be  fome  firm 
prop-work  interwoven  through  the  whole.  And, 
in  faft,  for  fuch  purpofes  the  bones'  are  given. 

The  prop-work  mufi:  not  be  made  into  one 
rigid  fabric,  for  that  would  prevent  motion. 
Therefore  there  are  a number  of  bones. 

Thefe  pieces  muft  ail  be  firmly  bound  toge- 
ther, to  prevent  their  diflccation.  And  this  end 
is  perfectly  well  anfwered  by  the  ligaments. 

The  extrematies  of  thefe  bony  pieces,  where 
they  move  and  rub  upon  one  another,  muft  have 
fmooth  and  flippery  furfaces  for  eafy  motion. 

This 


44  INTRODUCTION. 

This  is  moft  happily  provided  for,  by  the  carti- 
lages and  mucus  of  the  joints. 

The  interftices  of  all  thofe  parts  muft  be  filled 
up  with  fome  foft  and  ductile  matter,  which  fhall 
keep  them  in  their  places,  unite  them,  and  at 
the  fame  time  allow  them  to  move  a little  upon 
one  another.  And  thefe  purpofes  are  anfwered 
by  the  cellular  membrane  or  adipofe  fubftance. 

There  muft  be  an  outward  covering  over  the 
whole  apparatus,  both  to  give  it  compaftnefs  and 
to  defend  it  from  a thoufand  injuries  : which,  in 
fad;,  are  the  very  purpofes  of  the  fkin  and  other 
integuments. 

Laftly,  the  mind  being  formed  for  fociety  and 
intercourfe  with  beings  of  her  own  kind,  fhe 
muft  be  endued  with  powers  of  expreffing  and 
communicating  her  thoughts  by  fome  fenfible 
marks  or  figns  ; which  iliall  be  both  ealy  to  her- 
felf,  and  admit  of  great  variety  ; and  according- 
ly fhe  is  provided  with  the  organs  and  faculty  of 
fpeech,  by  which  fhe  can  throw  out  figns  with 
amazing  facility,  and  vary  them  without  end. 

Thus  we  have  built  up  an  animal  body  which 
would  feem  to  be  pretty  complete : but  as  it  is 
the  nature  of  matter  to  be  altered  and  worked 
upon  by  matter ; fo  in  a very  little  time  fuch  a 
living  creature  muft  be  deftroyed,  if  there  is  no 
provifion  for  repairing  the  injuries  which  fhe 
muft  commit  upon  herfeif,  and  thofe  which  fhe 
muft  be  expofed  to  from  without.  Therefore  a 
treafure  of  blood  is  adually  provided  in  the  heart 

and 


INTRODUCTION.  45 

and  vafcular  fyftem,  full  of  nutritious  and  heal- 
ing particles,  fluid  enough  to  penetrate  into  the 
minutefl:  parts  of  the  animal ; impelled  by  the 
heart,  and  conveyed  by  the  arteries,  it  waflies 
every  part,  builds  up  what  was  broken  down, 
and  Iweeps  away  the  old  and  ufelefs  materials. 
Hence  we  fee  the  necelTity  or  advantage  of  the 
heart  and  arterial  fyftem. 

What  more  there  was  of  this  blood  than 
enough  to  repair  the  prefent  damages  of  the  ma- 
chine, muft  not  be  loft,  but  Ihouid  be  teturned 
again  to  the  heart ; and  for  this  purpofe  the  ve- 
nous fyftem  is  actually  provided.  Thefe  requi- 
fites  in  the  animal  explain,  a priori^  the  circula- 
tion of  the  blood. 

The  old  materials  which  were  become  ufelefs, 
and  are  fwept  off  by  the  current  of  blood,  muft 
be  feparated  and  thrown  out  of  the  fyftem. 
Therefore  glands,  the  organs  of  Secretion,  are 
given  for  ftraining  whatever  is  rudundant,  vapid, 
or  noxious,  from  the  mafs  of  blood  ; and  when 
ftrained,  they  are  thrown  out  by  emunfLOries, 
called  organs  of  Excretion. 

But  now,  as  the  machine  muft  be  coiiftantly 
wearing  the  reparation  muft-  be  carried  on  with- 
out intermiflion,  and  the  ftraiiiers  muft  always 
be  employed.  Therefore  there  is  adlually  a per- 
petual circulation  of  the  blood,  and  the  fecretions 
are  always  going  on. 

Even  all  this  provifion,  however,  would  not 
be  fufhcient ; for  that  ftore  of  blood  v/ould  loon 

be 


a6  introduction. 

be  confumed,  and  the  fabric  would  break  down, 
if  there  were  not  a provifion  made  for  frefh  fup- 
plies.  Thefe  we  obferve,  in  fa£t,  are  profufely 
Icattered  round  her  in  the  animal  and  vegetable 
kingdoms  ; and  Ihe  is  furnifhed  with  hands,  the 
fitteft  inftruments  that  could  have  been  contrived, 
for  gathering  them,  and  for  preparing  them  in  a 
variety  of  ways  for  the  mouth. 

But  thefe  fupplies,  which  we  call  food,  muft 
be  confiderably  changed  ; they  muft  be  convert- 
ed into  blood.  Therefore  fhe  is  provided  with 
teeth  for  cutting  and  bruifmg  the  food,  and  with 
a ftomach  for  melting  it  down  : In  fhort,  with 
all  the  organs  fubfervient  to  digeftion.  The  finer 
parts  of  the  aliments  only  can  be  ufeful  in  the 
conftitution  : thefe  muft  be  taken  up  and  con- 
veyed into  the  blood,  and  the  dregs  muft  be 
thrown  off.  With  this  view  the  inteftinal  canal 
is  adually  given.  It  feparates  the  nutritious 
part,  which  vre  call  chyle^  to  be  conveyed  into 
the  blood  by  the  fyftem  of  abforbent  veflels  ; and 
the  feces  pafs  downwards,  to  be  conduded  out 
of  the  body. 

Now  we  have  got  our  animal  not  only  furniftr- 
ed  with  what  is  wanted  for  its  immediate  exift- 
ence,  but  alfo  Vv^ith  the  powers  of  protrading  that 
exiftence  to  an  indefinite  length  of  time.  But  its 
duration,  we  may  prefume,  muft  neceffarily  be 
limited : for  as  it  is  nourifhed,  grows,  and  is 
raifed  up  to  its  full  ftrength  and  utinoft  perfedion ; 
fo  it  muft,  in  time,  in  common  with  all  material 

beings, 


INTRODUCTION.  47 

beings,  begin  to  decay,  and  then  hurry  on  to  fi- 
nal ruin.  Hence  we  fee  the  neceffity  of  a fcheme 
for  renovation.  Accordingly  vfife  Providence, 
to  perpetuate  as  well  as  preferve  his  work,  be- 
fides  giving  a ftrong  appetite  for  life  and  felf-pre- 
fervation,  has  made  animals  male  and  female, 
and  given  them  fuch  organs  and  pafiions  as  will 
fecure  the  propagation  of  the  fpecies  to  the  end 
of  time. 

Thus  we  fee,  that  by  the  veiy  imperfedl  fur- 
vey  which  human  reafon  is  able  to  take  of  this 
fubjedl,  the  animal  man  muft  necelfarily  be 
complex  in  his  corporeal  fyftem,  and  in  its  ope- 
rations. 

He  muft  have  one  great  and  general  fyftem, 
the  vafcular,  branching  through  the  whole  for  cir- 
culation ; Another,  the  nen-ous,  with  its  append- 
ages the  organs  of  fenfe,  for  every  kind  of  feel- 
ing : And  a third,  for  the  union  and  connexion 
of  all  thofe  parts. 

Befides  thefe  primary  and  general  fyftems,  he 
requires  others  v/hich  may  be  more  local  or  con- 
fined : One  for  ftrength,  fiipport,  and  protection ; 
the  bony  compages  : Another  for  the  requifite 
motions  of  the  parts  among  themfelves,  as  well 
as  for  moving  from  place  to  place  ; the  raufcu- 
lar  part  of  the  body  : Another  to  prepare  nourifh- 
ment  for  the  daily  recruit  of  the  body  ; the  di- 
geftive  organs  : And  one  for  propagating  the  fpe- 
cies ; the  organs  of  generation. 

And  in  taking  this  general  furvey  of  what 

would 


48  INTRODUCTION, 
would  appear,  a prkri^  to  be  neceffary  for  adapt- 
ing an  animal  to  the  fituations  of  life,  we  obferve, 
with  great  fatisfadtion,  that  man  is  accordingly 
made  of  fuch  fyftems,  and  for  fuch  purpofes. 
He  has  them  all ; and  he  has  nothing  more,  ex- 
cept the  organs  of  refpiration.  Breathing  it 
feemeth  difficult  to  account  for  a priori  : we  only 
knew  it  to  be  in  fadt  effentially  neceffary  to  life. 
Notwithftanding  this,  when  we  faw  all  the  other 
parts  of  the  body,  and  their  functions,  fo  well 
accounted  for,  and  fo  wifely  adapted  to  their  fe- 
veral  purpofes,  there  could  be  no  doubt  that  ref- 
piration was  fo  likewife  : And  accordingly,  the 
difcoveries  of  Dr  Prieftley  have  lately  thrown 
light. upon  this  fundtion  alfo,  as  will  be  fhown  in 
its  proper  place. 

Of  all  the  different  fyftems  in  the  human  bo- 
dy, the  ufe  and  neceffity  are  not  more  apparent, 
than  the  wifdom  and  contrivance  which  has  been 
exerted  in  putting  them  all  into  the  moft  com- 
padl  and  convenient  form  ; in  difpofmg  them  fo, 
that  they  fhall  mutually  receive,  and  give  helps 
to  one  another ; and  that  all,  or  many  of  the 
parts,  fhall  not  only  anfwer  their  principal  end 
or  purpofe,  but  operate  fuccefsfully  and  ufefully 
in  a variety  of  fecondary  ways. 

If  we  confider  the  whole  animal  machine  in 
this  light,  and  compare  it  with  any  machine  in 
vrhich  human  art  has  exerted  its  utmoft  j fup- 
pofe  the  beft  conftrudled  ffiip  tha‘:  ever  was  built, 
xve  fttali  be  convinced  beyond  the  poffibility  of 
0.  doul  t. 


INTRODUCTION.  49 
doubt,  that  there  are  intelligence  and  power  far 
furpaffing  what  humanity  can  boaft  of. 

One  fuperiority  in  the  natural  machine  is  pe- 
culiarly ftriking.  In  machines  of  human  con- 
trivance or  art,  there  is  no  internal  power,  no 
principle  in  the  machine  itfelf,  by  which  it  can 
alter  and  accommodate  itfelf  to  any  injury  which 
it  may  fuffer,  or  make  up  any  injury  which  ad- 
mits of  repair.  But  in  the  natural  machine,  the 
animal  body,  this  is  moft  wonderfully  provided 
for,  by  internal  powers  in  the  machine  itfelf; 
many  of  which  are  not  more  certain  and  obvious 
in  their  elfedts,  than  they  are  above  all  human 
comprehenfion  as  to  the  manner  and  means  of 
their  operation.  Thus,  a wound  heals  up  of  it- 
felf ; a broken  bone  is  made  firm  again  by  a cal- 
lus ; a dead  part  is  feparated  and  thrown  off ; 
noxious  juices  are  driven  out  by  fome  of  the 
emundlories  ; a redundancy  is  removed  by  fome 
fpontaneous  bleeding ; a bleeding  naturally  flops 
of  itfelf ; and  a great  lofs  of  blood,  from  any 
caufe,  is  in  fome  meafure  compenfated,  by  a con- 
trading  power  in  the  vafcular  fyftem,  which  ac- 
commodates the  capacity  of  the  veffels  to  the 
quantity  contained.  The  flomach  gives  informa- 
tion when  the  fupplies  have  been  expended  ; re- 
prefents,  with  great  exadnefs,  the  quantity  and 
the  quality  of  what  is  wanted  in  the  prefent  ftate 
of  the  machine  ; and  in  proportion  as  fhe  meets 
with  neged,  rifes  in  her  demand,  urges  her  pe- 
tition in  a louder  tone,  and  with  more  forcible 
D arguments. 


50  INTRODUCTION, 
arguments.  For  its  protedion,  an  animal  bo- 
dy refifts  heat  and  cold  in  a very  wonderful 
manner,  and  preferves  an  equal  temperature  in  a 
burning  and  in  a freezing  atmofphere. 

A farther  excellence  or  fuperiority  in  the  na- 
tural machine,  if  poflible,  ftill  more  aftonifhing, 
more  beyond  ail  human  comprehenfion,  than 
■\yhat  we  have  been  fpealdng  of,  is  the  follow- 
ing Befides  thofe  internal  powers  of  felf-pre- 
fervation  in  each  individual,  when  two  of  them 
co-operate,  or  ad  in  concert,  they  are  endued 
with  powers  of  making  other  animals  or  ma- 
chines like  themfelves,  which  again  are  polfelfed 
of  the  fame  powers  of  producing  others,  and  fo 
of  multiplying  the  fpecies  without  end. 

Thefe  are  powers  which  mock  all  human  in- 
vention or  imitation.  They  are  charaderiftics 
of  the  divine  Archited. 

Having  premifed  this  general  account  of  the 
fubjed,  we  fhall  next  ^onfider  the  method  to  be 
obferved  in  treating  it. 

The  ftudy  of  the  human  body,  as  already  no- 
ticed, is  commonly  divided  into  two  parts.  The 
hrft,  which  is,  called  Anatomy^  relates  to  the  mat- 
ter and  ftrudure  of  its  parts  ; the  fecond,  called 
Phyfwlogy  and  Ajiimal  ceconomy^  relates  to  the 
principles  and  lavv^s  of  its  internal  operations  and 
fundions. 

As  the  body  is  a compound  of  folids  and  fluids, 
yjuatomy^  is  divided  into, 

I . The  Anatomy  of  the  folids,  and 


51 


INTR  ODtJCTION. 

2.  The  Anatomy  of  the  fluids. 

I.  The  Solids,  by  which  we  mean  all  parts 
of  oUr  body,  which  are  not  fluid,  are  generally 
divided  into  two  clalfes,  viz. 

1.  The  hard  folids  or  bones.  This  part  of 
anatomy  is  called  OJIeology  ; which  fignifies  the 
doctrine  of  the  bones. 

2.  The  fofter  folids ; which  part  is  called 
Sarcology,  viz.  the  doftrine  of  flefli. 

This  divifion  of  the  folids,  we  may  obferve, 
has  probably  taken  its  origin  from  the  vulgar  ob- 
fervation,  that  the  body  is  made  of  bone  and 
fiefh.  And  as  there  are  many  different  kinds  of 
what  are  called  foft  or  flefhy  parts,  Sarcology  is 
fubdivided  into, 

(i.)  Angeiology^  of  the  dodirine  of  veflels  ; by 
which  is  commonly  underftood  blood  vejfels  : 

(2.]  Adenology^  of  glands: 

(3.)  Neurology^  of  nerves: 

(4.)  Myology^  of  mufcles  : and, 

(3.)  Splanchnology^  of  the  vifcera  or  bowels. 
There  is,  befides,  that  part  which  treats  of  the 
organs  of  fenfe  and  of  the  integuments. 

This  divifion  of  the  folids  has  been  here  men- 
tioned, rather  for  the  fake  of  explaining  fo  ma- 
ny words,  which  are  conftantly  ufed  by  anato- 
mifts,  than  for  its  importance  or  accuracy.  For 
befides  many  other  objedtions  that  might  be  urg- 
ed, there  are  in  the  body  three  fpecies  of  folids, 
viz.  griftle  or  cartilage,  hair,  and  nails ; which 
are  of  an  intermediate  nature  between  bone  and 

D2  flefh; 


52  INTRODUCTION, 
flefh ; and  therefore  cannot  fo  properly  be 
brought  into  the  ofteology  or  the  farcology.  The 
cartilages  were  claffed  with  the  bones  ; becaufe 
the  greateft  number  of  them  are  appendages  to 
bones  : and  for  the  like  reafon  the  hair  and  the 
nails  were  claffed  with  the  integuments. 

II.  The  FLUIDS  of  the  human  body  may  be 
divided  into  three  kinds,  which  Dr.  Hunter  calls 
the  crude ^ the  general  or  perfect ^ and  the  local 
or  fecreted fluid. 

1.  By  \h.Q  crude  fluid  is  meant  the  chyle,  and 
whatever  is  abforbed  at  the  furface  of  the  body, 
in  other  words,  what  is  recently  taken  into  the 
body,  and  is  not  yet  mixed  with  or  converted 
into  blood. 

2.  The  general  or  perfeEl  fluid  is  the  blood 
itfelf,  to  wit,  what  is  contained  in  the  heart, 
arteries,  and  veins,  and  is  going  on  in  the  round 
of  the  circulation. 

3.  The  local  or  fecreted  are  thofe  fluids  pe- 
culiar to  particular  parts  of  the  body,  which 
are  ftrained  off  from  the  blood,  and  yet  are  very 
different  in  their  properties  from  the  blood.  They 
are  commonly  called  fecretions  ; and  fomeare 
ufeful,  others  excrementitious. 

In  treating  of  the  Phyfiology.^  it  is  very  diffi- 
cult to  fay  what  plan  fhould  be  followed ; for 
eveiy  method  which  has  been  yet  propofed,  is 
attended  with  manifeft  inconvenience.  The 
powers  and  operations  of  the  machine  have  fuch 
a dependence  upon  one  another,  fuch  connec- 
tions 


INTRODUCTI  ON.  53 
tions  and  reciprocal  influerxe,  that  they  cannot 
well  be  underflood  or  explained  leparately.  In 
this  fenfe  our  body  may  be  compared  to  a 
circular  chain  of  powers,  in  which  nothing 
is  firll  or  iaft,  nothing  folitary  or  indepen- 
dent ; fo  that  wherever  we  begin,  we  find 
that  there  is  fomething  preceding  which  we 
ought  to  have  known.  If  we  begin  with  the 
brain  and  the  nerves,  for  example,  we  fhall 
find  that  thefe  cannot  exift,  even  in  idea,  with- 
out the  heart : if  we  fet  out  with  the  heart  and 
vafcular  fyftem,  we  fhall  prefently  be  fenfible, 
that  the  brain  and  nerves  muft  be  fuppofed  : or, 
fhould  we  take  up  the  mouth,  and  follow  the 
courfe  of  the  aliment,  we  fhould  fee  that  the  very 
firft  organ  which  prefents  itfelf,  fuppofes  the 
exiftence  of  both  the  heart  and  the  brain  : v/here- 
fore  we  fhall  incorporate  the  Phyfiology  with 
the  Anatomy,  by  attempting  to  explain  the 
functions  after  we  have  demonfttated  the  or- 
gans. 


PART  I. 


54 


OSTEOLOGY. 


Part  L 


PARTI. 

OSTEOLO  G Y. 

W E begin  with  the  bones,  which  may  be 
confidered  as  the  great  fupport  of  the  body,  tend- 
ing to  give  it  fnape  and  firmnefs.— But  before 
v/e  enter  into  the  detail  of  each  particular  bone, 
it  will  be  neceffary  to  defcribe  their  compofition 
and  connections,  and  to  explaiu  the  nature  of 
the  different  parts  which  have  an  immediate  re- 
lation to  them ; as  the  cartilages,  ligaments, 
periofteum,  marrow,  and  fynovial  glands. 

Sect.  I.  Of  the  Bones  in  general y vijith  their 
appendagesy  &c. 

The  bones  are  of  a firm  and  hard  (b)  fub'’ 
fiance,  of  a white  colour,  and  perfectly  infen- 
fible.  They  are  the  moft  compad:  parts  of  the 
body,  and  ferve  for  the  attachment  and  fupport 
of  all  the  other  parts. 

Three  different  fubftances  are  ufually  diftin- 
guifiied  in  them ; their  exterior  or  bony  part, 
properly  fo  called  ; their  fpongy  cells  ; and  their 

reticular 

(b)  Mr.  Scheele  has  lately  difcovered  that  bones  contain 
the  phofphnric  add  united  v.'ith  calcareous  earth  ; and  that 
to  this  combination  they  owe  their  firmnefs. 


Part  I.  O S t E O L Q G T.  5^ 

reticular  fubftaiice.  . The  firft  of  thefe  is  form- 
ed of  tnany  lafnih^  or  plates,  compofmg  a firm 
hard  fiibftance^Thd  ]^ngy  or  cfelhilar  part  is 
fo  called  ofi  account  of  its  refemblan.ee  to  a fponge, 
from  the  little  cells  which  compofe  it.  This 
fubftance  forms  almoft  the  v/ncle  of  the  extre- 
mities of  cylindrical  bones.  The  reticular  part 
is  compofed  of  fibres,  which  crofs  each  other 
in  different  directions.  This  net-’^ork  forms 
the  internal  furface  of  thofe  bones  which  have 
cavities. 

The  flat  bones,  as  thofe  of  the  head,  are  com- 
pofed only  of  the  laminse  and  the  cellular  fub- 
ftance.  This  lafl;  is  ufually  found  in  the  middle 
of  the  bone  dividing  it  into  two  plates,  and  is 
there  called  diploe. 

Gagliardi,  who  pretended  to  have  difeovered 
an  infinite  number  of  claviculi  (c).,  or  bony 
proceffes,  which  he  deferibes  as  traverfmg  the  la- 
minae to  unite  them  together,  has  endeavoured 
to  fupport  this  pretended  difeovery  by  the  ana- 
logy of  bones  to  the  bark  of  trees,  in  which  cer- 
tain woody  nails  have  been  remarked  ; but  this 
opinion  feems  to  be  altogether  fanciful. 

Some  writers  have  fuppofed,  that  the  bones 
are  formed  by  layers  of  the  periofteum,  which 
gradually  offify,  in  the  fame  manner  as  the  tim- 
ber is  formed  in  trees  by  the  hardening  of  the 

white 

(c)  In  his  opium  nov.  invent,  iliuprat.  he  deferibes 

four  kinds  of  thefe  clavieuli  or  nails,  viz.  the  perpendicular, 
oblique,  headed,  and  crooked. 


S6  OSTEOLOGY,  Part  1, 

white  fubftance  that  is  found  between  the  inner 
bark  and  the  wood.  M.  Duhamel,  who  has 
adopted  this  opinion,  fed  different  animals  with 
madder  and  their  ordinary  food  alternately  du- 
ring a certain  time  ; and  he  afTerts,  that  in  dif- 
fedting  their  bones,  he  conftantly  obferved  dif- 
tinft  layers  of  red  and  white,  which  correfponded 
with  the  length  of  time  they  they  had  lived  on 
madder  or  their  ufual  aliment.  But  it  has  fince 
been  proved  by  Detleff,  that  M.  Duhamel’s  ex- 
periments were  inaccurate,  and  that  neither  the 
periofteum  nor  the  cartilages  are  tinged  by  the  ufe 
of  madder,  vvhich  is  known  to  affedt  the  bones 
only. 

We  ufually  confider  in  a bone,  its  body  and 
its  extremities.  The  ancients  gave  the  name  of 
diaphyfis  to  the  body  or  middle  part,  and  divi- 
ded the  extremities  into  apophyfis  and  epiphyfis. 
An  apophyfis,  or  procefs,  as  it  is  more  common- 
ly called,  is  an  eminence  continued  from  the  bo- 
dy of  the  bone,  whereas  an  epiphyfis  is  at  flrft  a 
fort  of  appendage  to  the  bone,  by  means  of  an 
intermediate  cartilage.  Many  epiphyfes,  which 
appear  as  diftlndt  bones  in  the  foetus,  afterwards 
become  apophyfes ; for  they  are  at  length  fo  com- 
pletely united  to  the  body  of  the  bone  as  not  to 
be  difiiinguifhable  from  it  in  the  adult  ftate.  It 
is  not  unufual,  however,  at  the  age  of  1 8 and 
even  20  years,  to  find  the  extremities  of  bones, 
ftill  in  the  ftate  of  epiphyfis. 

The  names  given  to  the  proceffes  of  bones 

are 


Part  I.  OSTEOLOGY.  57 

are  expreffive  of  their  fliape,  fize,  or  ufe  ; thus 
if  a procefs  is  large  and  of  a fpherical  form,  it  is 
called  caput ^ or  head;  if  the  head  is  flatted,  it 
is  termed  ccjidyle.  Some  proceffes,  from  their 
refemblance  to  a ftiletto,  a breaft,  or  the  beak  of 
a crow,  are  called  f.yloid^  nwjioid^  or  coracoid : 
others  are  ftyled  ridges  or fpines.  The  tw^o  pro^ 
celfes  of  the  os  femoris  derive  their  name  of 
trochanters  from  their  ufe. 

A bone  has  its  cavities  as  well  as,  proceflTes. 
Thefe  cavities  either  extend  quite  Through  its 
fubftance,  or  appear  only  as  depreflTicns.  The 
former  are  called  foramina  or  holes ^ and  thefe  ' 
foramina  are  fometimes  termed  canals  or  conduits^ 
according  to  their  form  and  extent.  Of  the  de- 
preflions,  fome  are  ufeful  in  articulation.  Thefe 
are  called  cotyloid  when  they  are  deep,  as  is  the 
cafe  with  the  os  innominatum,  where  it  receives 
the  head  of  the  os  femoris  ; ox  glenoid  when  they 
are  fuperficial,  as  in  the  fcapula,  where  it  re- 
ceives os  humeri.  Of  the  depreflTions  that  are 
not  defigned  for  articulation,  thofe  which  have 
fmall  apertures  are  called  finufes ; others  that  are 
large,  and  not  equally  Surrounded  by  high  brims, 
are  ftyled  fojfa ; fuch  as  are  long  and  narrow, 
furrows ; or  if  broad  and  fuperficial  without 
brims,  finuofities.  Some  are  called  digital  im- 
prejfions^  from  their  refemblance  to  the  traces  of 
a finger  on  foft  bodies. 

We  Ihall  abridge  this  article,  which  is  exceed-- 
ingly  diffufe  in  the  generality  of  anatomical 

books. 


58  O S T E O L O G Y.  Part  I. 

books,  and  will  endeavour  to  delcribe  it  with  all 
the  cleamefs  it  will  allow. 

The  BONES  compoling  the  fl?:eleton  are  fo  eon'* 
ftrufted,  that  the  end  of  every  bone  is  perfect- 
ly adapted  to  the  extremity  of  that  with  which  it 
is  connected,  and  this  connection  forms  what  is 
called  their  articiilatmi. 

Articulation  is  divided  into  diarthrojis ^ fynar- 
throjis^  and  amphiarthrofis^  or  moveable,  im- 
moveable, and  mixed  articulation.  Each  of  the 
two  iirft  has  its  fubdivifions.  Thus  the  Diar- 
tbrofis^  or  moveable  articulation,  includes,  i . The 
enarthrofis,  as  it  is  called,  when  a large  head  is 
admitted  into  a deep  cavity,  as  in  the  articula-^ 
tion  of  the  os  femoris  with  the  os  innominatum. 
2.  Arthrodia,  when  a round  head  is  articulated 
with  a fupeficial  cavity,  as  is  the  cafe  of  the  os 
humeri  and  fcapula.  3.  Ginglimus,  or  hinge- 
like articulation,  as  in  the  connexion  of  the 
thigh-bone  with  the  tibia.  The  enarthrofis  and 
arthrodia  allow  of  motion  to  all  fides  ; the  gin- 
glimus only  of  flexion  and  extcnfion. 

The  fynartbrofis^  or  immoveable  articulation, 
includes,  i.  The  future,  when  the  two  bones 
are  indented  into  each  other,  as  is  the  cafe  with 
the  parietal  bones.  2.  Gomphofis,  when  one 
bone  is  fixed  into  another,  in  the  manner  the 
teeth  are  placed  in  their  fockets. 

The  term  amplnartbrofis  is  applied  to  tiiofe 
articulations  which  partake  both  of  the  fynar- 
throfis  and  diarthrofis,  as  is  tlie  cafe  with  the 

boeris 


Part  I.  OSTEOLOGY.  59 

bones  of  tli,e  veitebrse,  which  are  capable  of  mo- 
tjqn  in  a ee-rtain  degree,  although  they  are.  firm- 
ly connected  together  by  intermediate  carti- 
lages. . 

What  is  called  fymphjfis  is  the  union,  of  two 
bones  into  one  ; as  in  the  lower  .jaw-,  for  in- 
ftance,  which  in  the  foetus,  confifts  o£  two  dif- 
tinft  bones,  but  becomes  one  in  a more  advanc- 
ed age,  by  the  offification  of  the  uniting  carti- 
lage. 

When  bone-s,  are  thus  joined  by  the.  means  of 
cartilages,  the  union  is  ^j\^ijy'n;hojidrofis  ; when 
by  ligaments,  fyneurofts. 

Cartilages  are  white,  foiid,  fmooth,  and 
elaftic  fubftances,  between  the  hardnefs  ci'  bones 
and  ligaments,  and  feemingly  of  a fibrous  tex- 
ture. We  are  not  able  to  trace  any  ve.fie's  into 
their  fubftance  by  injeflion,  nor  are  they  evex 
found  tinged  in  animals  thai,  have  been  fed 
with  madder. 

They  may  be-  diftingiiifhed  into,  in.  Thcfe 
which  aae  connected  with  the  bones ; and  2dly, 
Thofe  which  belong  to  other  parts  of  the  body. 
The  firft  ferve  either  to  cover  the  ends  and  ca- 
vities of  bones  intended  for  motion,  as  in  the 
articulations,  where  by  their  fmootfinefs  they  fa- 
cilitate motions,  which  the  bones  alone  could  not 
execute-  with  fo  much  freedom  ; or  they  ferve 
to  unite  bones  together,  as  in  the  fymphyfis  pu- 
bis, or  to  lengthem  them,  as  in  the  ribs. 

Many  of  them  offifying  as  we  advance  in  life. 


6o  OSTEOLOGY.  Part  I.  ? 

their  number  is  lefs  in  the  adult  than  in  the  fcetus,  * 
and  of  courfe  there  are  fewer  bones  in  the  old ' 
than  in  the  young  fubjedt.  | 

Of  the  fecond  clafs  of  cartilages  or  thofe  be- 
longing to  the  foft  parts,  we  have  inftances  in 
the  larynx,  where  we  find  them  ufeful  in  the 
formation  of  the  voice,  and  for  the  attachment 
of  mufcles. 

The  PERIOSTEUM  is  a fine  membrane  of  a 
compadt  cellular  texture,  reflected  from  one  joint 
to  another,  and  ferving  as  a common  covering,  to 
the  bones.  It  has  fanguiferous  and  lymphatic 
vefiels,  and  is  fupplied  with  nerves  from  the 
neighbouring  parts.  It  adheres  very  firmly  to 
their  furface,  and  by  its  fmoothnefs  facilitates  the 
motion  of  mufcles.  It  likewife  fupports  the  vef- 
fels  that  go  to  be  diftributedlhrough  the  fubftance 
of  the  bones,  and  may  ferve  to  ftrengthen  the 
articulations.  At  the  extremities  of  bones,  where 
it  is  found  covering  a cartilage,  it  has  by  fome 
been  improperly  confidered  as  a diftindl  mem- 
brane, and  named  perichondrium.  This,  in  its 
life  and  ftmdture,  refembles  the  periofteum. 
Where  it  covers  the  bones  of  the  Ikull,  it  has 
gotten  the  name  of  pericranium. 

The  periofteum  is  not  a produdtion  of  the  dura 
mater,  as  the  ancients,  and  after  them  Havers, 
imagined  ; nor  are  the  bones  formed  by  the  olli- 
fication  of  this  membrane,  at  leaft  when  it  is  in 
a found  ftate,  as  fome  late  writers  have  fuppofed. 


the 


Part  I.  OSTEOLOGY.  6i 

the  fockets,  and  in  thofe  parts  of  bones  to  which 
ligaments  or  tendons  are  attached. 

The  MARROW  is  a fat  oily  fubftance,  filling 
the  cavities  of  bones.  In  the  great  cavities  of 
long  bones  it  is  of  much  firmer  confiftence  than 
in  the  cells  of  their  fpongy  part.  In  the  former 
it  inclines  fomewhat  to  a yellowifli  tinge,  and 
is  of  the  confiftence  of  fat ; in  the  latter  it  is 
more  fluid,  and  of  a red  colour.  This  diffe- 
rence in  colour  and  confiftence  is  owing  to  ac- 
cidental caufes  ; both  kinds  are  of  the  fame  na- 
ture, and  may  both  be  defcribed  under  the  com- 
mon name  of  marrow,  though  fome  writers  give 
the  name  only  to  the  fat-like  fubftance,  and  call 
the  other  the  medullary  juice. 

The  marrow  is  contained  in  a very  fine  and 
tranfparent  membrane,  which  is  fupplied  with  a 
great  number  of  blood  veffels,  chiefly  from  the 
periofteum.  This  membrana  medullaris  adheres 
to  the  inner  furface  of  the  bones,  and  furnifhes 
an  infinite  number  of  minute  bags  or  veficles 
for  inclofing  the  marrow,  which  is  likewife  fup- 
ported  in  the  cavities  of  the  bones  by  the  long 
filaments  of  their  reticular  fubftance. 

Befides  the  veffels  from  the  periofteum,  the 
membrana  medullaris  is  furnifhed  with  others, 
which  in  the  long  bones  may  be  feen  palling  in 
near  the  extremities  of  the  bone,  and  fending  off 
numerous  branches  that  ramify  through  all  the 
veficles  of  this  membrane. 

The  bones,  and  the  cells  containing  the  mar- 
row 


62  OSTEOLOGY.  pAJLt  I. 

row,  are  likewife  fiirnifhed  with  lyrtiphatics.  By 
their  means,  the  marrow,  like  the  fat,  tnay  be 
taken  up  in  a greater  quantity  than  it  is  fecreted ; 
and  hence  it  is  that  fo  little  are  found  in  the  bones 
of  thofe  who  die  of  lingering  difeafes. 

It  is  ftill  a matter  of  contrOverfy,  Whether 
the  marrow  is  fenlible  or  not  ? We  are  certaiii'- 
ly  not  able  to  trace  any  nerves  to  it ; and  from 
this  circurnhaiiGe,  and  its  analogy  to  fat,  Haller 
has  ventured  to  confider  it  as  infeiifible.  Oh  the 
other  hand,  Duverney  aiTerts,  that  an  injury 
done  to  this  fubftance  in  a living  animal  was  at- 
tended with  great  pain.  In  this  difpute  phyfi- 
ologifts  do  not  feem  to  have  fufficiently  difcri- 
minated  between  the  m_arrow  itfelf  and  the  mem- 
branous cells  in  which  it  is  contained.  The 
former,  like  the  fat,  being  nothing  more  than  a 
fecreted,  and  of  courfe  an  inorganized,  matter, 
may  with  propriety  be  ranked  among  the  infenli- 
ble  parts,  as  much  as  infpiflated  mucus  or  any 
other  fecreted  matter  in  the  body  ; whereas  the 
membrana  medullaris  being  vafcular,  though  it 
poffeffes  but  an  obfcure  degree  of  feeling  in  a 
found  ftate,  is  not  perfedtly  infenfible. 

The  marrow  was  formerly  fuppofed  to  be  in- 
tended for  the  nourifhment  and  renewal  of  the 
bones  ; but  this  dodrine  is  now  ptetty  generally 
and  defervedly  exploded.  It  feems  probable  that 
the  marrow  is  to  the  bones  what  fat  is  to  the  foft 
parts.  They  both  ferve  for  fome  important  pur- 
pofes  in  the  animal  oecoxiomy ; but  their  parti- 
cular 


Part  L OSTEOLOGY.  63 

cular  life  has  ne-veryet  been  clearly  afceitained. 
The  marrow,  from  the  tranfudation  of  the  oil 
through  the  bones  of  a fkeleton,  is  iuppofed  to 
diminiih  th|^ir  brittlenefs ; and  Havers,  who 
has  written  profefledly  on  the  bones,  defcribes 
the  canals  by  which  the  marrow  is  conveyed 
through  every  part  of  their  fubftance,  and  di- 
vides them  into  longitudinal  and  tranfverfe  ones. 
He  fpeaks  of  the  firft  as  extending  tlirough  the 
whole  length  of  the  bone  ; and  of  the  latter,  as 
the  palfages  by  which  the  longitudinal  ones  com- 
municate vrith  each  other.  The  fimiliarity  of 
thefe  to  the  large  cancelli  in  burnt  bones,  and 
the  tranfudation  of  the  oil  through  the  bones  of 
the  fkeleton,  feems  to  prove  that  fome  fuch  paf- 
fages  do  adtually  exift. 

The  SYNOVIAL  GLANDS  are  fmall bodies  (d), 
fuppofed  to  be  of  a glandular  l^frudture,  and  ex- 
ceedingly vafcular,  fecreting  a fluid  of  a clear  mu- 
cilaginous nature,  which  ferves  to  lubricate  the 
joints.  They  are  placed  in  fmall  cavities  in  the 
articulations,  fo  as  to  be  capable  of  being  gently 
compreffed  by  the  motion  of  the  joint,  which  ex- 
preffes  their  juice  in  proportion  to  the  degree  of 
fridtion.  When  the  fynovia  is  wanting,  or  is  of 
too  thick  a CDiififtence,  the  joint  becomes  ftiff 

and 

(d)  It  is  now  much  doubted,  however,  whether  the  ap- 
pearances in  the  joints,  which  are  ulually  called  glands^  are 
any  thing  more  than  aiTemblages  of  fat. 


64  OSTEOLOGY.  Part  I. 

and  incapable  of  flexion  or  extenfion.  This  is 
what  is  termed  anchylojis. 

Ligaments  are  white,  gliftening,  inelaftic 
bands,  of  a compa(St  fubftance,  more  or  lefs 
broad  or  thick,  and  ferving  to  conned;  the  bones 
together.  They  are  diftinguifhed  by  different 
names  adapted  to  their  different  forms  and  ufes. 
Thofe  of  the  joints  are  called  either  round  or 
burfal.  The  round  ligaments  are  white,  tendi- 
nous, and  inefaftic.  They  are  ffrong  and  flexi- 
ble, and  are  found  only  in  the  joint  of  the  knee, 
and  in  the  articulation  of  the  osfembris  with  the 
os  innominatum.  The  burfal,  or  capfular  liga- 
ments, furround  the  whole  joint  like  a purfe,  and 
are  to  be  found  in  the  articulations  which  allow 
motion  every  way,  as  in  the  articulation  of  the 
arm  with  the  fcapula. 

Of  thofe  facs  called  Bursje  mucosa,  a few 
were  known  to  former  anatomifls,  but  by  much 
the  greater  number  have  been  fmce  difcovered  by 
Dr.  Monro  (e),  who  obferves,  that  they  are  to 
be  met  with  in  the  extremities  of  the  body  on- 
ly ; that  many  of  them  are  placed  entirely  on 
the  inner  fides  of  the  tendons,  between  thefe 
and  the  bones.  Many  others  cover  not  only  the 
innner,  but  the  outer  fides  of  the  tendons, 
or  are  interpofed  between  the  tendons  and 
external  parts,  as  well  as  between  thofe  and  the 
bones. 

3 Some 


(e)  See  Dcfcription  of  the  Burfce  Mucofe^  See. 


Part  % OSTEOLOGY.  6$ 

■ Some  arefituated  between  the  tendofi^  and  exr 
ternal  parts  onVy  or  chieflyy  fome  between  con- 
tiguous tendons,  or  between  the  tendons  or  thi 
ligaments  and  the  joints.  A few  fuch  facs  are 
ebferved  where  the  proceffes  of  bonds'  play  upon 
the  ligaments,  or  where  one  bone  plays  upori 
another.  Where  two  or  rbore  tendonsrare  cOn-' 
tiguous,  and  afterwards  f^arate  from  each  othefy 
we  generally  find  a common  burfa  di'vkJed  inte> 
branches,  with  which  it  communicates and  § 
fewbnrfsd  of  contiguous  tendons  epmmUnicate 
with  each  other.-"=^ome-y  in  healthy  childrdn,- 
eommtmicate  with  the-  Cavities  of  the-  joints ; 
and  m many  oM  people  he  has  feen  fueh  com- 
munications formed  by  ufo  or  worn  by  fridlioh. 
Independent-  of  difeafe. 

Their  proper  membrane  is  thin  and  tranfpa-* 
renty  bnt  very  denfe  and  capable  of  confining 
air  or  any  other  fiuid.'  It  is  joined  to  the  neigh- 
bouring^ parts  by  tile  common  cellular  fubftanee.- 
Betweeen  the  burfa  and-  the  hardr  fubftanee  of 
bone,  a thin-  layer  of  cartilage  or  Of  tough  mem-' 
brane  is  ve-ry  ggnerally  interpofed.  To  the  cel- 
lular fubftanee  on  the  oiitfide  of  the  burfa,  the 
adipofe  fiibftance-  is  Gonne<fted;  except  where 
the  burfa  covers  a tendon,  cartilage,  or  bone, 
much  eifpofed  to  prefiure  or  fridion. 

In  feveral  places  a mafs  of  fat,  covered  with 
the  continuation  of  the  membrane  of  the  burfa, 
projects  into  its  cavity.  The  edges  of  this  are 
divided  into  fringes. 


E 


The 


66  OSTEOLOGY.  Part  I. 

The  inner  fide  of  the  membrane  is  fmooth, 
and  is  extremely  flippery  from  the  liquor  fecret- 
ed  in  it. 

The  ftrudture  of  the  burfae  bears  a ftrong  re- 
femblance  to  the  capfular  ligaments  of  the  joints. 
I . The  inner  layer  of  the  ligament,  like  that  of 
the  burfas,  is  thin  and  denfe.  2.  It  is  connedted 
to  the  external  ligaments  by  the  common  cellu- 
lar fubftance.  3.  Between  it  and  the  bones,  lay- 
ers of  cartilage,  or  the  articular  cartilages,  are  in- 
terpofed.  4.  At  the  Tides  of  the  joints,  where 
it  is  not  fubjedt  to  violent  preffure  and  fridlion, 
the  adipofe  fubftance  is  connected  with  the  cel- 
lular membrane.  5.  Within  the  cavities  of  the 
joints  we  obferve  mafles  of  fat  projedling,  cover- 
ed with  fimilar  blood-veflels,  and  with  fimilar 
fimbrise  hanging  from  their  edges.  6.  In  the 
knee  the  upper  part  of  fuch  a mafs  of  fat  forms 
what  has  been  called  the  jmfcilaginous  gland  of 
the  joints  and  the  under  part  projects  into  the 
burfa  behind  the  ligament  which  ties  the  patella 
to  the  tibia.  7.  The  liquor  which  lubricates  the 
burfse  has  the  fame  colour,  confiftence,  and  pro- 
perties as  that  of  the  joints,  and  both  are  affedled 
in  the  fame  manner  by  heat,  mineral  acids,  and 
ardent  fpirits.  8.  In  fome  places  the  burfe  con- 
ftantly  communicate  with  the  cavities  of  the 
joints,  in  others  they  generally  do  fo  ; from 
which  we  may  infer  a famenefs  of  ftrudxure. 

When  we  examine  the  ftmbri;^  common  to 
the  fatty  bodies  of  the  joints  and  burfe,  and 
which  have  been  fuppofed  to  be  the  dudfs  of  glands 

lodged 


Part  I.  OSTEOLOGY.  67 

lodged  within  the  mafles  of  fat,  we  are  not  able 
to  difcover  any  glandular  appearance  within 
them.  And  although  we  obfenm  many  veffels 
difperfed  upon  the  membranes  of  the  fatty  bo- 
dies and  fimbrisE  ; and  that  we  cannot  doubt  that 
thefe  fimbrise  confift  of  ducTs  which  contain  a 
lubricating  liquor,  and  can  even  prefs  fuch  a li- 
quor from  them  ; yet  their  cavities  and  orifices 
are  fo  minute,  that  they  are  not  difcoverabie 
even  by  the  afliftance  of  magnifying-glalfes. 
Thefe  fimbrise  appear,  therefore,  to  be  dudts 
like  thofe  of  urethra,  which  prepare  a mucila- 
inous  liquor  without  the  afliftance  of  any  knotty 
gr  glandular  organ. 

Upon  the  whole,  the  fynovia  feems  to  be  fur- 
niftied  by  invifible  exhalent  arteries  by  the  dudls 
of  the  fimbrise,  and  by  oil  exuding  from  the  adi- 
pofe  follicles  by' paffages  not  yet  difcovered. 

The  word  Jkcleton^  which  by  its  etymology 
fimply  implies  a dry  preparation,  is  ufually  ap- 
plied to  an  aflTemblage  of  all  the  bones  of  an 
animal  united  together  in  their  natural  order. 
It  is  faid  to  be  a natural  fkeleton,  when  the  bones 
are  connected  together  by  their  own  proper  li- 
gaments ; and  an  artificial  one,  when  they  are 
joined  by  any  other  fubftance,  as  wire,  &c. 

The  fkeleton  is  generally  divided  into  the 
head,  trunk,  and  extremities.  The  firft  divifion 
includes  the  bones  of  the  cranium  and  face. 
The  bones  of  the  trunk  are  the  fpine,  ribs,  fter- 
num,  and  bones  of  the  pelvis. 

E 2 \ 


The 


6S  OSTEOLOGY.  Part  I. 

The  upper  extremity  on  each  fide  confifts  of 
the  two  bones  of  the  fhoulder,  viz.  the  fcapula 
and  clavicle ; the  bone  of  the  airm,  or  os  hu- 
meri j the  bones  of  the  fore-arm,  and  thofe 
of  the  hand. 

The  lower  extremity  on  each  fide  of  the  trunk 
confifts  of  the  thigh-bones  and  the  bones  of  the 
leg  and  foot. 

Sect.  II.  Of  the  Bones  of  the  Head. 

The  head  is  of  a roundifti  figure,  and  fome- 
what  oval  (p).  Its  greateft  diameter  is  from  the 
forehead  to  the  occiput ; its  upper  part  is  called 
•vertex^  or  crown  of  the  head ; its  anterior  or 
fore-part  the  face ; and  the  upper  part  of  this 
fmdputy  or  forehead  ; its  fides  the  temples  ; its 
pofterior,  or  hind-part,  the  occiput ; and  its  in- 
ferior part  the  laps. 

The  bones  of  the  head  may  be  divided  into 
tliofe  of  the  cranium  and  face. 

§ I Boffci 

(lO  The  bones  of  the  foetus  being  perfedlly  diftinfl,,  and 
the  muicles  in  young  perfons  not  afting  much,  the  fliape  of 
the  head  has  been  fuppofed  to  depend  much  on  the  manage- 
ment of  children  when  very  young.  Vefalius,  who  has 
remarked  the  difference  in  people  of  different  nations,  ob- 
ierves,  for  inftance,  that  the  head  of  a Turk  is  conical, 
from  the  early  ufe  of  the  turban  j v/hilft  that  of  an  EugUfh- 
man  is  flattened  by  the  chin-ftay.  Some  of  tlie  lateft  phy- 
fiolog'illu  fuppofe,  with  good  reafon,  that  this  difference  is 
chiefly  owing  to  certain  natural  caufes  with  which  we  are  as, 
vet  unacquainted. 


Part  I. 


OSTEOLOGY. 


69 


§ I.  Bones  of  the  Cranium  and face. 

There  are  eight  bones  of  the  cranium,  viz.  the 
coronal  bone,  or  os  frontis ; the  two  parietal 
bones  ; or  offa  bregmatis  ; the  os  occipitis ; the 
two  temporal  bones  ; the  fphenoid  bone  j and  the 
os  ethmoides,  or  cribriforme. 

Of  thefe,  only  the  os  occipitis  and  ofla  breg- 
matis are  coniidered  as  proper  to  the  cranium  ; 
the  reft  being  common  both  to  the  cranium  and 
face. 

Thefe  bones  are  all  harder  at  their  furface  than 
in  their  middle  ; and  on  this  account  they  are 
divided  into  two  tables,  and  a middle  fpongy 
fubftance  called  dtploe. 

Os  Frontis.  In  this,  as  in  all  other  bones,  we 
ftiall  confider  its  figure,  ftrudnre,  procefles,  de- 
preffions  and  cavities  ; and  the  manner  in  which 
it  is  articulated  with  the  other  bones. 

The  os  fronds  has  fome  refemblance  in  fhape 
to  the  ftiell  of  the  cockle.  Externally  it  is  con- 
vex, its  concave  fide  being  turned  towards  the 
brain.  This  bone,  in  the  places  where  it  is  uni- 
ted to  the  temporal  bones,  is  very  thin,  and  has 
there  no  diplde.  It  is  likewife  exceedingly  thin 
in  that  part  of  the  orbit  of  the  eye  winch  is 
neareft  to  the  nofe.  Hence  it  is,  that  a wound 
in  the  eye,  by  a fword  or  any  other  pointed  in- 
ftrument,  is  fometimes  productive  of  immedi- 
ate death.  In  thefe  cafes, the  fword  pafling  through 

the 


70  OSTEOLOGY.  Part  I, 

the  weak  part  of  the  bone,  penetrates  the  brain, 
and  divides  the  nerves  at  their  origin  ; or  per- 
haps opens  fome  blood-veffei,  the  confequences 
of  which  are  foon  fatal. 

We  obferve  on  the  exterior  furface  of  this 
bone  five  apophyfes  or  procefles,  which  are  ear- 
fily  to  be  diflinguiflied.  One  of  thefe  is  placed 
at  the  bottom  and  narroweft  part  of  the  bone, 
and  is  called  the  nafal  procefs,  from  its  fupport- 
ing  the  upper  end  of  the  bones  of  the  nofe. 
The  four  others  are  called  angular  or  orbitar  pro- 
cefles. They  affift  to  form  the  orbits,  which 
are  the  cavities  on  which  the  eyes  are  placed.  In 
each  of  thefe  orbits  there  are  two  proceffes,  one 
at  the  interior  or  great  angle,  and  the  other  at 
the  exterior  or  little  angle  of  the  orbit.  They 
are  called  the  angular  proceffes.  Between  thefe 
a ridge  is  extended  in  form  of  an  arch,  and  on 
this  the  eye-brows  are  placed.  It  is  called  the 
orbitar  or  fuperciliary  ridge,  and  in  fome  mea- 
fiire  covers  and  defends  the  globe  of  the  eye. 
There  is  a hole  in  this  for  the  paffage  of  the 
frontal  veffels  and  nerves.  This  arch  is  inter- 
rupted near  the  nofe  by  a fmail  pit,  in  which'  the 
tendon  of  the  mufculus  obliquus  major  of  the 
eye  is  fixed.  From  the  under  part  of  each  fu- 
perciliary ridge  a thin  plate  runs  a confiderable 
way  backwards,  and  has  the  name  of  orbitar ; 
the  external  and  fore-part  of  this  plate  forms  a 
finuofity  for  lodging  the  lacrymal  gland.  Betv/een 
the  orbitar  plates  there  is  a large  dilcontinuation 


PartT.  osteology.  71 

of  the  boiie,  which  is  filled  up  by  the  cribriform 
part  of  the  os  ethmoides. 

On  examining  the  inner  furface  of  this  bone 
at  its  under  and  middle  part,  we  obferve  an  ele- 
vation in  form  of  a ridge,  which  has  been  called 
the  fpinous procefs  ; it  afcends  forfome  way,  di- 
viding the  bone  into  two  confiderable  foflse,  in 
which  the  anterior  lobes  of  the  brain  are  placed. 
To  a narrow  furrow  in  this  ridge  is  attached  the 
extremity  of  the  falx,  as  the  membrane  is  called, 
which  divides  the  brain  into  two  hemifpheres. 
The  furrow  becoming  gradually  wider,  is  conti- 
nued to  the  upper  and  back  part  of  the  bone.  It 
has  the  falx  fixed  to  it,  and  part  of  the  longitudi- 
nal finus  lodged  in  it.  Befides  the  two  foflse, 
there  are  many  deprefiions,  which  appear  like 
digital  impreffions,  • and  owe  their  formation  to 
the  prominent  circumvolutions  of  the  brain. 

In  the  foetus,  the  forehead  is  compofed  of  two 
diftind;  bones  ; fo  that  in  them  the  fagittal  future 
reaches  from  the  os  occipitis  to  the  nofe.  This 
bone  is  almofl;  every  where  compofed  of  two  ta- 
bles and  a diploe.  Thefe  two  tables  feparating 
from  each  other  under  the  eyes,  form  two  cavi- 
ties, one  on  each  fide  of  the  face,  called  the 
frontal  finufes.  Thefe  fmufes  are  lined  with  a 
foft  membrane,  called  membrana  pituitaria.  In 
thefe  finufes  a mucus  is  fecreted,  which  is  con- 
ftantly  paffing  through  two  fmall  holes  into  the 
noftrils,  which  it  ferves  to  moiften. 

The  os  frontis  is  joined  by  future  to  many  of 

the 


19  S T E O L O a Y.  ?A%T  !. 
tji€  feo^ies  of  th,e  Jiea4,  yi?.  to  thf  p^fletgl,  maX‘» 
illary,  and  temporal  bones ; to  the  o.s  ethmoides } 
OS  Ipl^eopides ; o§  ungojs  ; and  ojia  mf^r  The 
future  which  .copned^s  it  with  the  parietal  bones 
is  called  the  forqn^l  futurt^, 

The  PARipiTAP  SQNps  are  twa  in  number; 
they  are  very  thin,  and  even  tranfparent  ip  fame 
places,.  The  particular  figure  of  each  of  thefe 
hones  is  that  pf  an  irregular  fquare,  bordered  with 
indentations  through  its  whole  circumference,  ex- 
cept at  jts  lower  part.  It  will  be  eafily  conceiv- 
ed, that  thefe  bones  which  eompofe  the  fuperior 
and  lateral  parts  of  the  cranium,  and  cover  the 
greateft  part  of  the  brain,  form  a kind  of  vault. 
On  their  inner  fiirface  we  obferve  the  marks  of 
the  veffels  pf  the  dura  mater ; and  at  their  upr- 
per  edge  the  groove  for  the  iuperior  longitudinal 
fmus. 

The  olTa  parietalia  are  joined  to  each  other 
by  the  fagittal  future ; to  the  ps  fphenoides 
and  offa  tempprum  by  the  fquamous  future ; 
to  the  os  OGcipitis  by  the  lambdoidai  future  (a), 
fo  called  from  its  refemblance  to  the  Greek  letter 
lambda ; and  to  the  ps  firputis  by  the  coronal  fu? 
tore. 

In  the  foetus,  the  parietal  bones  are  feparated 
from  the  middle  of  the  divided  os  frontis  by  a 
portion  of  tfie  cranium  then  unoffified. 

The 

(a)  The  lambdoidai  future  is  Ibmetimes  very  irregular,  be- 
ing compofed  of  many  fmall  futures,  which  furround  fo  many 
little  bones  called  ojfa  triquetra^  though  perhaps  improperly, 
as rhey  are  jiot  always  triangular. 


Part  I.  OSTEOLOGY. 

The  OCCIPITAL  BONE  forms  the  pofterior 
and  inferior  parts  of  the  Ikull ; it  approaches 
nearly  to  the  fhape  of  a lozenge,  and  is  indented 
throughout  three  parts  of  its  circumference. 

There  is  a confiderable  hole  in  the  inferior 
portion  of  this  bone,  called  the  foramen  magniLWf^ 
through  which  the  medulla  oblongata  pafles  into 
the  fpine.  The  nervi  accelTorii,  and  vertebral 
arteries,  like  wife  pafs  through  it.  Behind  the 
condyles  are  two  holes  for  the  palTage  of  cervical 
veins  into  the  lateral  finufes ; and  above  them 
are  two  others  for  the  paflage  of  the  eighth  pair 
and  accelTory  nerves  out  of  the  head.  At  the 
fides,  and  a little  on  the  anterior  part  of  the  fora- 
men magnum,  are  two  procefles,’ called  the  con- 
dyles, one  on  each  fide ; they  are  of  an  oval  fi- 
gure, and  are  covered  with  cartilage. 

The  external  furface  of  this  bone  Jias  a large 
tranfverfe  arched  ridge,  under  which  the  bone  is 
very  irregular,  where  it  affords  attachment  to  fe- 
veral  mufcles.  On  examining  its  inner  furface, 
we  may  obferve  two  ridges  in  form  of  a crofs ; 
one  afcending  from  near  the  foramen  magnum  to 
the  top  of  the  bone  ; the  upper  end  of  this  in 
which  the  falx  is  fixed,  is  hollow,  for  lodging 
the  fuperior  longitudinal  finus,  and  the  under  end 
has  the  third  procefs  of  the  dura  mater  fixed  to 
it.  The  other  ridge,  which  runs  horizontally, 
is  likewife  hollow  for  containing  the  lateral  finufes. 
Four  foffse  are  formed  by  the  crofs,  two  above 
and  two  below.  In  the  former  are  placed  the  pof- 

terior 


^4  O S T E O L O G Y.  Part  I. 

terlor  lobes  of  the  brain,  and  in  the  latter  the  lobes 
of  the  cerebellum. 

At  the  bafis  of  the  cranium,  we  obferve  the 
cuneiform  procefs  (which  is  the  name  given  to 
the  great  apophyfis  at  the  fore  part  of  this  bone) ; 
it  ferves  for  the  reception  of  the  medulla  oblon- 
gata. 

The  os  occipitis  is  of  greater  ftrength  and 
thicknefs  than  either  of  the  other  bones  of  the 
head,  though  irregularly  fo  : at  its  inferior  part, 
where  it  is  thinneft,  it  is  covered  by  a great  num- 
ber of  mufcles. 

This  bone,  from  its  fituation,  being  more  lia- 
ble to  be  injured  by  falls,  than  any  other  bone 
of  the  head,  nature  has  wifely  given  it  the  greateft 
ftrength  at  its  upper  part,  where  it  is  moft  expof- 
ed  to  danger. 

It  is  joined  to  the  parietal  bones  by  the  lamb- 
doidai  future,  and  to  the  offa  temporum,  by  the 
additaraentum  of  the  temporal  future.  It  is  like- 
wife  connefted  to  the  os  fphenoides.by  the  cunei- 
form procefs.  It  is  by  means  of  the  os  occipitis 
that  the  head  is  united  to  the  trunk,  the  two  con- 
dyles of  this  bone  being  connedled  to  the  fupe- 
rior  oblique  proceffes  of  the  firft  vertebra  of  the 
neck. 

There  are  two  temporal  bones,  one  on  each 
ftde. — ^\Ve  may  diftinguifli  in  them  two  parts; 
one  of  which  is  called  the  fquamous  ovfcaly  part^ 
and  the  other^^rr  pctroja  from  its  hardnefs.  This 
laft  is  ftiaped  like  a pyramid. 


Each 


Part  I.  OSTEOLOGY.  75 

Each  of  thefe  divifions  affords  proceffes  and  ca- 
vities : externally  there  are  three  proceffes  ; one 
anterior,  called  the  zygomatic  procefs  , one  pos- 
terior, called  the  77wJloid  or  mamillary  procefs^ 
from  its  refemblance  to  a nipple ; and  one  infe- 
rior, called  the  Jiylold  procefs^  becaufe  it  is  fliaped 
like  a ftiletto,  or  dagger. 

The  cavities  are,  i . The  meatus  aiiditorius  ex- 
temus.  2.  A large  foffa  which  ferv^es  for  the  ar- 
ticulation of  the  lower  jaw  ; it  is  before  the  mea- 
tus auditorius,  and  immediately  under  the  zygo- 
matic procefs.  3.  The  ftylo-maftoid  hole,  fo 
called  from  its  fituation  between  the  ftyloid  and 
maftoid  proceffes  ; it  is  likevrife  fcyled  the  aqus- 
du£b  of  Fallopius,  and  affords  a paffage  to  the 
portio  dura  of  the  auditory,  or  feventh  pair  of 
nerves.  4.  Belowg  and  on  the  fore-pait  of  the 
laft  foramen,  we  obferve  part  of  the  jugular  folia, 
in  which  the  beginning  of  the-  internal  jugular 
vein  is  lodged.  Anterior  and  fuperior  to  this 
foffa  is  the  orifice  of  a foramen,  through  which, 
paffes  the  carotid  artery.  This  foramen  runs  firft 
upwards  and  then  forwards,  forming  a kind  of 
elbow,  and  terminates  at  the  end  of  the  os  pe- 
trofum. — At  this  part  of  each  temporal  bone,  we 
may  obfeire  the  opening  of  the  Euftachian  tube, 
a canal  which  paffes  from  the  ear  to  the  back  part 
of  the  nofe. 

In  examining  the  internal  furface  of  thefe 
bones,  we  may  remark  the  triangular  figure  of 
their  petrous  part  which  feparates  two  foffse  ; one 

fuperior 


76  OSTEOLOGY.  Part  L 

fuperior  and  anterior  ; the  other  inferior  and 
pofterior : the  latter  of  thefe  cpmpofcs  part  of 
the  foffa,  in  which  the  cerebellum  is  placed  ; 
and  the  former,  a portion  of  the  leaft  folTa  for 
the  bafis  of  the  brain.  On  the  pofterior  fide  of 
the  pars  petrofa,  we  obferve  the  meatus  auditorus 
inteiVms,  into  which  enters  the  double  nerve  of 
the  fcventh  pair.  Oh  the  under  fide  of  this  pro- 
cefs,  part  of  a hole  appears,  which  is  common 
to  the  temporal  and  occipital  bones ; through  it 
ftie  lateral  fmus,  the  eighth  pair,  and  acceftbry 
nerves,  pafs  out  of  the  head. 

The  pars  petrofa  contains  feveral  little  bones 
called  the  bones  of  the  ear ; which,  as  they  do 
not  enter  into  the  formation  of  the  cranium,  ftiall 
be  defcribed  when  we  are  treating  of  the  organs 
of  hearing. 

The  ofla  temponim  are  joined  to  theoffa  ma- 
famm,  by  the  zygomatic  futures ; to  the  pa- 
rietal bones,  by  the  fquamous  futures ; to  the 
os  occipitis,  by  the  lambdoidal  future ; and  to 
ihe  fphenoid  bone,  by  the  future  of  that  name. 

Os  fphenoldes.  This  bone,  from  its  fituation 
amidft  the  other  bones  of  the  head,  has  fometimes 
been  called  cuneiforme.  It  is  of  a very  irregular 
figure,  and  has  been  compared  to  a bat  with  its 
wings  extended. 

It  is  commonly  divided  into  its  middle  part  or^ 
body,  and  its  fides  or  wings. 

The  fore  part  of  the  body  has  a fpine  or  ridge, 
which  makes  part  of  the  feptum  narium.  The 

upper 


Part  I.  OSTEOLOGY.  77 

Upper  part  of  each  wing  forms  a fhare  of  the 
temple.  The  fore  part  of  this  belongs  to  the  or- 
bit ; while  the  under  and  back  part,  termed 
Jpinous  procefs^  is  lodged  in  the  bafe  of  the  ikuil 
at  the  point  of  the  pars  petrofa.  But  two  of  the 
moft  remarkable  proceffes  are  the  ptergoid  or  ali- 
form, one  on  each  fide  of  the  body  of  the  bone, 
and  at  no  great  diftance  from  it.  Each  of  thefe 
proceffes  is  divided  into  two  wings,  and  of  the^ 
the  exterior  one  is  the  wideft.  The  other  ter- 
minates in  a hook-like  procefs. 

The  internal  furface  of  this  bone  aflbrds  three 
foffsB.  Two  of  thefe  are  formed  by  the  wings 
of  the  bone,  and  make  a part  of  the  leffer  foflk: 
of  the  balls  of  the  cranium.  The  third,  which 
b fmalier,  is  on  the  top  of  the  body  of  the  bone; 
and  is  called  fella  turcica^  from  its  refemblance 
to  a Turkilh  faddle.  This  foffa,  in  which  the 
pituitary  gland  is  placed,  has  pofteriorly  and  an- 
teriorly proceffes  called  the  dinoid proceffes. 

There  are  twelve  holes  in  this  bone,  viz.  fix 
on  each  fide.  The  firft  is  the  paffage  01  the  op^ 
tic  nerve  and  ocular  artery ; the  fecond,  or  large 
flit,  tranfmits  the  third,  fourth,  fixth,  and  firll 
part  of  the  fifth  pair  of  nerves  with  the  ocular 
vein ; the  third  hole  gives  paffage  to  the  fecond 
branch  of  the  fifth  pair  ; and  the  fourth  hole  to 
the  third  branch  of  the  fifth  pair  of  nerves.  The 
fifth  hole  is  the  paffage  of  the  artery  of  the  dura 
mater.  The  fixth  hole  is  fituated  above  the 
ptergoid  prqpefs  of  the  fphenoid  bone  ; through 


78  OSTEOLOGY.  Part  t 

It  a reflected  branch  of  the  fecond  part  of  the 
fifth  pairpafies. 

Within  the  fubftance  of  the'os  fphenoides  there 
are  two  finiifes  feparated  by  a bony  plate.  They 
are  lined  with  the  pituitary  membrane ; and, 
like  the  frontal  fmufes,  feparate  a mucus  which 
pafies  into  the  noftrils. 

The  os  fphenoides  is  joined  to  all  the 
bones  of  the  cranium  ; and  likewife  to  the 
offa  maxillaria,  ofia  malarum,  olTa  palati,  and 
vomer.  ' 

This  bone  makes  part  of  the  bafis  of  the  flcull, 
affifts  in  forming  the  orbits,  and  affords  -attach- 
ment to  feveral  mufcles. 

The  os  ethmoides  is  fituated  at  the  fore  part  of 
the  balls  of  the  cranium,  and  is  of  a very  irre- 
gular figure.  From  the  great  number  of  holes 
with  which  it  is  pierced,  it  is  fometimes  called  os 
crlbrlforme  or  fieve-like  bone 

j 

The  os  ethmoides  or  cribriforme  confifts  of  a 
middle  part  and  two  fides.  The  middle  part  is 
formed  of  a thin  bony  plate,  in  which  are  an 
infinite  number  of  holes  that  afford  a palfage  to 
filaments  of  the  olfailory  nerve.  From  the  mid- 
dle of  this  plate,  both  on  the  outfide  and  from 
within,  there  rifes  up  a procefs,  which  may  be 
cafily  diftinguifhed.  The  inner  one  is  called 
crijla  galli^  from  its  fuppofed  refemblance  to  a 
cock’s  comb.  To  this  procefs  the  falx  of  the 
dura  mater  is  attached.  The  exterior  procefs, 
which  has  the  fame  common  bafis  as  the  crifla 

galli, 


Part  I.  OSTEOLOGY.  79 

gain,  is  a fine  lamella  which  is  united  to  the 
vomer  ; and  divides  the  cavity  of  the  noftrils, 
though  unequally,  it  being  generally  a little  in- 
clined to  one  fide. 

The  lateral  parts  of  this  bone  are  compofed 
of  a cellular  fubftance  ; and  thefe  cells  are  lb  ve- 
ry intricate,  that  their  figure  or  number  cannot 
be  defcribed.  Many  -writers  have  on  this  account 
called  this  part  of  the  bone  the  labyrinth.  Thefe 
cells  are  externally  covered  with  a very  thin  bony 
lamella.  This  part  of  the  bone  is  called  the  os 
planum.^  and  forms  part  of  the  orbit. 

The  different  cells  of  this  bone,  which  are 
numerous,  and  which  are  every  where  lined  with 
the  pituitary  membrane,  evidently  ferv'^e  to  en- 
large the  cavity  of  the  nofe,  in  which  the  organ 
of  fmelling  refides. 

This  bone  is  joined  to  the  os  fphenoides,  os 
frontis,  offa  maxillaria,  offa  palati,  offa  nafi,  offa 
unguis,  and  vomer. 

The  ancients,  who  confidered  the  brcdn  as  the 
feat  of  all  the  humours,  ima.gined  that  this  vifcus 
difcharged  its  redundant  moifture  through  the 
holes  of  the  ethmoid  bone.  And  the  vulear  flili 
think,  that  abfceffes  of  the  brain  difcharge  them- 
felves  through  the  mouth  and  ears,  and  that  fniifi 
is  liable  to  get  into  the  head  ; but  neither  fiiuff 
nor  the  matter  of  an  abfcefs  are  more  capable  of 
paffing  through  the  cribriform  bone,  than  the 
ferofity  which  they  fuppofed  -^vas  difcharged 
through  it  in  a common  cold,— -All  the  holes  of 

th: 


8o  OSTEOLOGY.  Part  h 

the  ethmoid  bone  are  filled  Up  with  the  branches' 
of  the  ojfadory  nerve.  Its  iuner  part  is  likewife 

covered  with  the  dura  mater,  and  its  cells  are 
every  where  lined  with  the  pituitary  membrane ; 
fo  that  neither  matter  nor  any  other  3uid  can 
poffibly  pafs  through  this  bone  either  externally 
or  internally.  Matter  is  indeed  fometimes  dif^ 
charged  through  the  noftrils ; but  the  feat  of  the 
difeafe  is  in  the  finufes  of  the  nofe,  and  not  in 
the  brain  ; and  impofthumations  are  obferved  to 
take  place  in  the  ear,  which  fuppUrate  and  difs 
charge  themfelves  externally. 

Before  we  leave  the  bones  of  the  head,  we  wifh 
to  make  fome  general  obfervations  on  its  ftruc- 
ture  and  figure.  As  the  cranium  might  have 
been  compofed  of  a fingle  bone,  the  aTticulation. 
of  its  feveral  bones  being  abfolutely  without  mo- 
tion, it  may  be  afked  perhaps.  Why  fuch  a mul- 
tiplicity of  bones,  and  fo  great  number  of  fu- 
tures ? Many  advantages  may  poffibly  arife  from 
this  plurality  of  bones  and  futures,  which  may 
not  yet  have  been  obferved.  We  are  able,  how- 
ever, to  point  out  many  ufeful  ends,  which  cOuld 
only  be  accomplifhed  by  this  peculiarity  of  ftruc- 
ture. — In  this,  as  in  all  the  other  works  of  na- 
ture, the  great  wifdom  of  the  Creator  is  evinced, 
and  cannot  fail  to  excite  our  admiration  and  gra- 
titude. 

The  cranium,  by  being  divided  into  feveral 
bones,  grows  much  fafter  and  with  greater  faci- 
lity, than  if  it  was  compofed  of  one  piece  only. 

3 


Part  I.  OSTEOLOGY.  8i 

In  the  foetus,  the  bones,  as  we  have  before  oh- 
ferved,  are  perfectly  diftindf  from  each  other. 
The  offification  begins  in  the  middle  of  each 
bone,  and  proceeds  gradually  to  the  circumfer- 
ence. Hence  the  offification,  and  of  courfe  the 
increafe  of  the  head,  is  carried  on  from  an  infi- 
nite number  of  points  at  the  fame  time,  and  the 
bones  confequently  approach  each  other  in  the 
fame  proportion.  To  illuftrate  this  dodirine 
rnore  clearly,  if  it  can  want  further  illuftration,-.; 
fuppofe  it  neceffary  for  the  parietal  bones  which 
compofe  the  upper  part  of  the  head,  to  extend 
their  offification,  and  form  the  fore  part  of  the 
head  likewife. — Is  it  not  evident,  that  this  pro- 
cefs  would  be  much  more  tedious  than  it  is  now, 
when  the  os  fronds  and  the  parietal  bones  are 
both  growing  at  the  fame  time  ? Hence  it  hap- 
pens, that  the  heads  of  young  people,  in  which 
the  bones  begin  to  touch  each  other,  increafe 
flowly ; and  that  the  proportionate  increafe  of 
the  volume  of  the  head  is  greater  in  three  months 
in  the  foetus,  than  it  is  perhaps  in  twenty-four 
months  at  the  age  of  fourteen  or  fifteen  years. 

The  futures,  exclufive  of  their  advantage  in 
fufpending  the  proceffes  of  the  dura  mater,  are 
evidently  of  great  utility  in  preventing  the  too 
great  extent  of  fractures  of  the  Ikull. — Suppofe, 
for  inftance,  that  by  a fall  or  blow,  one  of  the 
bones  of  the  cranium  becomes  fradtured.  The 
fiffure,  which  in  a head  compofed  of  only  one 
bone,  would  be  liable  to  extend  itfelf  through 

F the 


82  OSTEOLOGY.  Part!. 

the  whole  of  it,  is  checked,  and  fometimes  per- 
haps hopped  by  the  firft  future  it  meets,  and  the 
effedls  of  the  injury  are  confined  to  the  bone  on 
which  the  blow  was  received.  Ruyfch  indeed, 
and  fome  others,  will  not  allow  the  futures  to  be 
of  any  fuch  ufe ; but  cafes  have  been  met  with 
where  they  feemed  to  have  had  this  elFe£t,  and 
in  young  fubjedts  their  utility  in  this  refpe£t  muft 
be  ftill  more  obvious. 

The  fpherical  fhape  of  the  head  feems  likewife 
to  render  it  more  capable  of  refilling  external  vi- 
olence than  any  other  fhape  would  do.  In  a 
vault,  the  parts  mutually  fupport  and  llrengthen 
each  other,  and  this  happens  in  the  cranium. 

§ 2.  Proper  Bones  of  the  Face. 

The  face,  which  confifts  of  a great  num- 
ber of  bones,  is  commonly  divided  into  the  up- 
per and  lower  jaws.  The  upper  jaw  confifts  of 
thirteen  bones,  exclufive  of  the  teeth.  Of  thefe, 
fix  are  placed  on  each  fide  of  the  maxilla  fuperior, 
and  one  in  the  middle. 

The  bones,  which  are  in  pairs,  are  the  ofla 
malarum,  ofia  maxillaria,  ofla  nafi,  oflTa  unguis, 
ofl'a  palati,  and  olTa  fpongiofa  inferiora.  The 
fingle  bone  is  the  vomer. 

The  o([a  malarum  are  the  prominent  fquare 
bones  which  are  placed  under  the  eyes,  forming- 
part  of  the  orbits  and  the  upper  part  of  the  cheeks. 
Each  of  them  affords  three  furfaces  ; one  exte- 
rior and  a little  convex  ; a fecond  fuperior  and 

concave. 


PartI.  osteology.  83 

jconeave,  forming  the  inferior  part  and  Tides  of 
the  orbit ; and  a third  pollerior,  irregular,  and 
hollowed  for  the  lodgement  of  the  lower  part  of 
the  temporal  mufcle. ' 

The  angles  of  each  bone  form  four  procelTes, 
two  of  which  may  be  called  orbitar  proeejfes  ; of 
thefe  the  npper  one  is  joined  by  future  to  the  os 
frontis,  and  that  below  to  the  maxillary  bone. 
The  third  is  connedled  with  the  os  fphenoideS 
by  means  of  the  tranfverfe  future  ; and  the  fourth 
is  joined  to  the  zygomatic  procels  of  the  tempo- 
ral bone,  with  which  it  forms  the  zygoma. 

The  ojfa  ma^illaria  fiiperiora,  Thefe  bones, 
which  are  of  a very  irregular  figure,  are  fo  called 
becaufe  they  form  the  moft  confiderable  por- 
tion of  the  upper  jaw.  They  are  two  in 
number,  and  generally  remain  diftin<5l  through 
life. 

Of  the  many  procelTes  which  are  to  be  feen 
on  thefe  bones,  and  which  are  conneded  with 
the  bones  of  the  face  and  Ikull,  we  lhall  defcribe 
only  the  moft  remarkable. 

One  of  thefe  procelTes  is  at  the  upper  and  fore 
part  of  the  bone,  making  part  of  the  fide  of  the 
nofe,  and  called  the  ?iafal procefs.  Another  forms 
a kind  of  circular  fweep  at  the  inferior  part  of  the 
bone,  in  which  are  the  alveoli  or  fockets  for  the 
teeth : this  is  called  the  alveolar  procefs.  A third 
procefs  is  united  to  the  os  malae  on  each  fide.  Be- 
tween this  and  the  nafal  procefs  there  is  a thin 
plate,  which  forms  a lhare  of  the  orbit,  and  lies 
F 1 over 


84  OSTEOLOGY.  Part  I. 

over  a pafTage  for  the  fuperior  maxillary  veffels 
and  nerves. — -The  alveolar  procefs  has  pofteriorly 
a confiderable  tuberofity  on  its  internal  furface, 
called  the  maxilla7~y  tuberojity. 

Behind  the  alveolar  procefs  we  obferve  two 
horizontal  lamellas,  which  uniting  together,  form 
a part  of  the  roof  of  the  mouth,  and  divide  it 
from  the  nofe.  The  hollownefs  of  the  roof  of 
the  mouth  is  owing  to  this  partition’s  being  feat- 
ed  fomewhat  higher  than  the  alveolar  procefs.-— 
At  the  fore  part  of  the  horizontal  lamellse  there 
is  a hole  called  foramen  inclfivum^  through  which 
fmall  blood-velfels  and  nerves  go  between  the 
mouth  and  nofe. 

In  viewing  thefe  bones  internally,  we  ob- 
ferve  a foffa  in  the  inferior  portion  of  the  nafal 
procefs,  which,  with  the  os  unguis  and  os  fpon- 
giofum  inferius,  forms  a pafTage  for  the  lachrymal 
du£t. 

Where  thefe  two  bones  are  united  to  each 
other,  they  projedf  fomewhat  upwards  and  for- 
wards', leaving  between  them  a furrow,  into 
which  the  lower  portion  of  the  feptum  nafi  is 
admitted. 

Each  of  thefe  bones  being  hollow,  a confider- 
able fmus  is  formed  under  its  orbitar  part.  This 
cavity,  which  is  ufually  named  after  Highmore, 
though  it  v^ras  defcribed  by  Fallopius  and  others 
before  his  time,  is  lined  with  the  pituitary  mem- 
brane. It  is  intended  for  the  fame  purpofes  as 

th€ 


Part!.  OSTEOLOGY.  S5 

the  other  finufes  of  the  nofe,  and  opens  into  the 
noftrils. 

The  ofla  maxillaria  are  connected  with  the 
greater  part  of  the  bones  of  the  face  and  crani- 
um, and  affift  in  forming  not  only  the  cheeks, 
but  likewife  the  palate,  nofe,  and  orbits. 

The  ojfa  Jiafi  form  two  irregular  fquares.  They 
are  thicker  and  narrower  above  than  below.  Ex- 
ternally they  are  fomewhat  convex,  and  inter- 
nally flightly  concave.  Thefe  bones  conftitutc 
the  upper  part  of  the  nofe.  At  their  fore  part 
they  are  united  to  each  other,  above  to  the  os 
frontis,  by  their  fides  to  the  olTa  maxillaria  fupe- 
riora,  pofteriorly  and  interiorly  to  the  feptum  na- 
rium,  and  below  to  the  cartilages  that  compofe 
the  reft  of  the  noftrils. 

The  oJfa  unguis.  Thefe  little  tranfparent 
bones  owe  their  name  to  their  fuppofed  refem- 
blance  to  a finger-nail.  Sometimes  they  are 
called  ojja  lachrymalia,  from  their  concurring 
with  the  nafal  procefs  of  each  maxillary  bone 
in  forming  a lodgement  for  the  lachrymal  fac  and 
du£t. 

The  ofla  unguis  are  of  an  irregular  figure. 
Their  external  furface  confifts  of  two  finooth 
parts,  divided  by  a middle  ridge.  One  of  thefe 
parts,  which  is  concave  and  neareft  to  the  nofe, 
ferves  to  fupportthe  lachrymal  fac  and  part  of  the 
lachrymal  dudt.  The  other,  which  is  flat,  forms 
a fmall  part  of  the  orbit. 


Each 


86  O S t E O L O G Y.  Part  I. 

Each  of  thefe  bories  is  conne<Si:ed  with  thtJ 
os  frontis,  os  ethmoides,  and  os  maxillare  fu- 
perius. 

The  ojfa  palati.  Thefe  bones,  which  are  fi- 
tuated  at  the  back  part  of  the  roof  of  the  mouthy 
between  the  os  fphenoides  and  the  olTa  inaxillaria 
fuperiora,  are  of  a very  irregular  thape,  and  ferve 
to  form  the  nafal  and  maxillary  fotfa^  and  a fmall 
portion  of  the  orbit.  Where  they  are  united  to 
each  other,  they  rife  up  into  a fpine  On  their  in^ 
ternal  furface.  This  fpine  appears  to  be  a con- 
tinuation of  that  of  the  fuperior  maxillary  bones, 
and  helps  to  form  the  feptum  narium. 

Thefe  bones  are  joined  tO  the  olfa  maxillaria 
fuper-i'ora,  os  ethmoides,  os  fphenoides,  and  vo- 
mer, 

The  vomer.  This  bone  derives  its  name  from 
its  refemblance  to  a ploughftiare.  It  is  a long 
and  flat  bone,  fomewhat  thicker  at  its  back  than 
at  its  fore  part.  At  its  upper  part  we  obferve  a 
furrow  extending  through  its  whole  length.  The 
pofterior  and  largeft  part  of  this  furrow  receives 
a procefs  of  the  fphenoid  bone.  From  this  the 
farrow  advances  forwards,  and  becorhing  nar- 
rower and  fhalloWer,  receives  fome  part  of  the 
nafal  larnella  ethmoidea ; the  reft  fer^es  to  fup- 
port  the  middle  cartilage  of  the  nofe. 

The  inferior  portion  of  this  bone  is  placed  on 
the  nafal  fpine  Of  the  maxillary  and  palate  bonOs, 
which  we  mentioned  in  our  defeription  of  the 
€)ffa  paiati. 


The 


Part  I.  OSTEOLOGY.  87 

The  vomer  is  united  to  the  os  fphenoides,  os 
ethmoides,  offa  maxillaria  fuperiora,  and  oiTa 
palati.  It  forms  part  of  the  feptum  nariurrv, 
by  dividing  the  back  part  of  the  nofe  into  two 
noftrils. 

The  ojja  fpongiofa  hiferiora.  The  parts  which 
are  ufually  defcribed  by  this  name,  do  not  feem 
to  deferve  to  be  diftinguifhed  as  diftind;  bones, 
except  in  young  fubjeds.  They  confift  of  a 
fpongy  lamella  in  each  noftril,  which  is  united 
to  the  fpongy  lamina  of  the  ethmoid  bone,  of 
which  they  are  by  fome  confidered  as  a pait. 

Each  of  thefe  lamellse  is  longeft  from  I ■ - 
hind  forwards  ; with  its  convex  furface  tmn- 
ed  towards  the  feptum  narium,  and  its  con 
cave  part  towards  the  maxillary  bone,  co- 
vering the  opening  of  the  lachrymal  dud  into 
the  nofe. 

Thefe  bones  are  covered  with  the  pituita- 
ry membrane  ; and,  befides  their  connedion 
with  the  ethmoid  bone,  are  joined  to  the  olTa 
maxillaria  fuperiora,  ofla  palati,  and  oifa  un- 
guis. 

The  maxilla  inferior^  or  lower  jaw,  which  in 
its  fhape  refembles  a horfe-lhoe,  confifts  of  two 
diftind  bones  in  the  foetus ; but  thefe  unite  to- 
gether|foon  after  birth,  fo  as  to  form  only  one 
bone.'  The  upper  edge  of  this  bone,  like  the  os 
maxillare  fuperius,  has  an  alveolar  procefs,  fur- 
niflied  with  fockets  for  the  teeth. 


On 


88  OSTEOLOGY.  Part  I. 

On  each  fide,  the  pofterior  part  of  the  bone 
rifes  almoft  perpendicularly  into  two  proceifes. 
The  higheft  of  thefe  called  the  coronoid  procefs, 
is  pointed  and  thin,  and  ferves  for  the  infertion 
of  the  temporal  mufcle.  The  other,  or  condy- 
loid procefs,  as  it  is  called,  is  Ihorter  and  thicker, 
and  ends  in  an  oblong  rounded  head,  which  is 
received  into  a foffa  of  the  temporal  bone,  and 
is  formed  for  a moveable  articulation  with  the 
cranium.  This  joint  is  furniflied  with  a move- 
able  cartilage.  At  the  bottom  of  each  coronoid 
procefs,  on  its  inner  part,  we  obferve  a foramen 
extending  under  the  roots  of  all  the  teeth,  and 
terminating  at  the  outer  furface  of  the  bone  near 
the  chin.  Each  of  thefe  canals  tranfmits  an  ar- 
tery, vein,  and  neiwe,  from  which  branches  are 
fent  off  to  the  teeth. 

The  lower  jaw  is  capable  of  a great  variety  of 
motion.  By  Hiding  the  condyles  from  the  cavi- 
ty towards  the  eminences  on  each  fide,  we  bring 
it  horizontally  forwards,  as  in  biting ; or  we 
may  bring  the  condyles  only  for^vard,and  tilt  the 
reft  of  the  jaw  backward,  as  in  opening  the 
mouth.  We  are  likewife  able  to  Aide  the  con- 
dyles alternately  backwards  and  forwards  from 
the  cavity  to  the  eminence,  and  vice  vcrfa^  as 
in  giinding  the  teeth.  The  cartilages,  b^^dapt- 
ing  themfelves  to  the  different  inequaf^s  in 
thefe  feveral  motions  of  the  jaw,  ferve  toYecure 
the  articulation,  and  to  prevent  any  injuries  from 
fri<ftion. 


Th.e 


Part  I.  OSTEOLOGY.  89 

The  alveolar  procefles  are  compofed  of  an 
outer  and  inner  bony  plate,  united  together  by 
thin  partitions,  which  at  the  fore  part  of  the 
jaw  divide  the  procefles  into  as  many  fockets  as 
there  are  teeth.  But  at  the  back  part  of  the  jav/, 
where  the  teeth  have  more  than  one  root,  we 
find  a difl;in<St  cell  for  each  root.  In  both  jaws 
thefe  procelTes  begin  to  be  formed  with  the 
teeth  ; they  likewife  accompany  them  in  their 
growth,  and  gradually  difappear  when  the  teeth 
are  removed. 

§ 3*  Teeth. 

TuETEETHare  bones  of  a particular  ftrudure, 
formed  for  the  purpofes  of  maftication  and  the 
articulation  of  the  voice.  It  will  be  necelfary  to 
confider  their  compofition  and  figure,  their  num- 
ber and  arrangement,  and  the  time  and  order  in 
which  they  appear. 

In  each  tooth  we  may  diftinguifh  a body,  a 
neck,  and  a root  or  fangs. 

The  body  of  the  tooth  is  that  part  which  ap- 
pears above  the  gums.  The  root  is  fixed  into 
the  focket,  and  the  neck  is  the  middle  part  be- 
tween the  two. 

The  teeth  are  compofed  of  two  fubflances, 
viz.  enamel  and  bone.  The  enamel,  or  the  vi- 
terous  or  cortical  part  of  the  tooth,  is  a white  and 
very  hard  and  compadi  fubftance  peculiar  to  the 
teeth,  and  appears  fibrous  or  ftriated  when  broken. 
This  fubftance  is  thickeft  on  the  grinding  fur- 

face, 


90  OSTEOLOGY.  Part  I.  ^ 

face,  and  becoming  gradually  thinner,  terminates 
infenfibly  at  the  neck  of  the  tooth.  Ruyfch  ^ 
affirmed,  that  he  could  trace  the  arteries  into  the 
hardeft  part  of  the  teeth  j Liewenhoeck  f fuf-  i 
pefted  the  fibres  of  the  enamel  to  be  fo  many 
vefTels  : and  Monro  X fays,  he  has  frequently  in- 
jefted  the  vefTels  of  the  teeth  in  children,  fo  as 
to  make  the  infide  of  the  cortex  appear  perfedily 
red.  But  it  is  certain,  that  it  is  not  tinged  by  a j 
madder  diet;  and  that  no  injection  will  ever 
reach  it,  fo  that  it  has  no  appearance  of  being 
vafcular  §. 

The  bony  part,  which  compofes  the  inner 
fubftance  of  the  body,  neck,  and  root  of  the 
tooth,  refembles  other  bones  in  its  ftrufture,  but 
it  is  much  harder  than  the  moft  compact  part 
of  bones  in  general.  As  a tooth  when  once 
formed  receives  no  tinge  from  a madder  diet, 
and  as  the  minuteft  injedtions  do  not  penetrate 
into  its  fubftance,  this  part  of  the  tooth  has,  like 
the  enamel,  been  fuppofed  not  to  be  vafcular. 

But  when  we  confider  that  the  fangs  of  a tooth 
are  invefted  by  a periofteum,  and  that  the  fwell-  | 
ings  of  thefe  fangs  are  analogous  to  the  iwellings 
of  other  bones,  we  may  reafonably  conclude, 
that  there  is  a fimilarity  of  ftrufture ; and  that 
this  bony  part  has  a circulation  througi  its  fub- 

ftanpe, 

* Thefaur  lo.  no.  27. 

Arcan.  Natur.  continuat.  Epiftol. 

-j  Anat.  of  the  Human  Bones. 

^ Hunter  on  the  Teeth. 


VajltL  osteology.  91 

ftancc,  although  from  its  hardueft  wg  are  unable 
to  demonftrate  its  veflels. 

In  each  tooth  we  find  an  inner  cavity,  into 
Tvhich  enter  an  artefy,  vein,  and  neiwe.  This 
cavity  begins  by  a fmall  opening,  and  becoming 
larger,  terminates  in  the  body  of  the  tooth.  In 
advanced  life  this  hole  fometimes  clofes,  and  the 
tooth  is  of  courfe  rendered  infenfible. 

The  periofteum  fiirrounds  the  teeth  from  their 
fengs  to  a little  beyond  their  bony  fockets,  where 
we  find  it  adhering  to  the  gums.  This  mem- 
brane, while  it  inclofes  the  teeth,  fei*ves  at  the 
fame  time  to  line  the  fockets,  fo  that  it  may  be 
confidered  as  common  to  both. 

The  teeth  are  likewife  fecured  in  their  fock- 
ets by  means  of  the  gums  ; a red,  vafcular,  firm, 
and  elaftic  fubftance,  that  polTeffes  but  little  fen- 
fibility.  In  the  gums  of  infants  we  find  a hard 
ridge  extending  through  their  whole  length,  but 
no  fuch  ridge  is  to  be  feen  in  old  people  who 
have  loft  tlieir  teeth. 

'The  number  of  the  teeth  in  both  jaws  at  full 
EMturity,  ufually  varies  from  tv/enty-eight  to 
tlmfy-two.  They  are  commonly  divided  into 
three  clafles,  viz.  incifores,  canini,  and  grind- 
ers or  molares  (h).  The  incifores  are  the  four 
teeth  imlae  fore  part  of  each  jaw.  They  have 

each 

Yh)  Mr,  Hunter  h>as  thought  proper  to  vary  this  divifion. 
Hwetaius  the  old  name  incifores  to  the  four  fore  teeth,  but 
he  diftinguifhes  the  canine  teeth  by  the  name  of  the  afpidati. 

The 


^2  OSTEOLOGY;  Part  h 

each  of  them  two  furfaces ; one  anterior  and 
convex,  the  other  pofterior  and  (lightly  concave, 
both  of  which  terminate  in  a lharp  edge.  They 
are  called  incifores  from  their  ufe  in  dividing  the 
food.  They  are  ufually  broader  and  thicker  in 
the  upper  than  in  the  under  jaw ; and,  by  be- 
ing placed  fomewhat  obliquely,  generally  fall 
over  the  latter. 

The  canini  derive  their  name  from  their  re- 
femblance  to  a dog’s  tulks,  being  the  longeft  of 
all  the  teeth.  We  find  one  on  each  fide  of  the 
incifores,  fo  that  there  are  two  canini  in  each 
jaw.  Their  fang  refembles  that  of  the  incifores, 
but  is  much  larger;  and  in  their  fhape  they  appear 
like  an  incifor  with  its  edge  worn  off,  fq  as  to 
terminate  in  a narrow  point. 

Thefe  teeth  not  being  calculated  for  cutting 
and  dividing  the  food  like  the  incifores,  or  for 
grinding  it  like  the  molares,  feem  to  be  intend- 
ed for  laying  hold  of  fubflances  (i). 

The  molares  or  grinders,  of  which  there  are 
ten  in  each  jaw,  are  fo  called,  becaufe  from  their 
fhape  and  fize  they  are  fitted  for  grinding  the 
food.  Each  of  the  incifores  and  canini  is  fur- 

nifhed 

‘‘The  two  teeth  which  are  next  to  thefe,  and  whicl^’'-<ave  beea 
ufually  ranked  with  the  molares,  he  calls  the  bicujpides  ; and 
he  frir^es  the  name  of  grinders  only  to  the  three  laft  teeth  on 
each  fide. 

(i)  Mr.  Hunter  remarks  of  thefe  teeth,  that  Wc  may  trace 
in  them  a fimilarity  in  fhape,  fituaticn,  and  ule,  from  the 
moft  imperfectly  carnivorous  animal,  which  we  believe  to  be 
the  human  fpecies,  to  the  lion,  which  is  the  mofi:  perfeftly 
carnivorous. 


Part  L OSTEOLOGY.  95 

niflied  only  with  one  fang  ; but  in  the  molares 
of  the  under  jaw  we  conftantly  find  two  fangs, 
and  in  thofe  of  the  upper  jaw  three  fangs.  Thefe 
fangs  are  fometimes  feparated  into  two  points, 
and  each  of  thefe  points  has  fometimes  been  de- 
fcribed  as  a diftind;  fang. 

The  two  firft  of  the  molares,  or  thofe  near- 
eft  to  the  canine  teeth  on  each  fide,  differ  from 
the  other  three,  and  are  with  great  propriety 
named  bicufpides  by  Mr.  Hunter.  They  have 
fometimes  only  one  root,  and  feem  to  be  of  a 
middle  nature  between  the  incifores  and  the 
larger  molares.  The  two  next  are  much  larger. 
The  fifth  or  laft  grinder  on  each  fide  is  fmaller 
and  fliorter  than  the  reft  ; and  from  its  not  cut- 
ting the  gum  till  after  the  age  of  twenty,  and 
fometimes  not  till  much  later  in  life,  is  called 
dens  faplentia. 

There  is  in  the  ftru£ture  and  arrangement  of 
all  thefe  teeth  an  art  which  cannot  be  fufficiently 
admired.  To  underhand  it  properly,  it  will  be 
neceflary  to  confider  the  under  jaw  as  a kind  of 
lever,  with  its  fixed  points  at  its  articulations  with 
the  temporal  bones : — it  will  be  right  to  obferve, 
too,  that  its  powers  arife  from  its  different  muf- 
cles,  but  in  elevation  chiefly  from  the  tempora- 
lis and  maffeter ; and  that  the  aliment  conftitutes 
the  objedt  of  refiftance.  It  will  appear,  then, 
that  the  molares,  by  being  placed  neareft  the  cen- 
tre of  motion,  are  calculated  to  prefs  with  a much 
greater  force  than  the  other  teeth,  independent 
©f  their  grinding  powers  which  they  poflefs  by 

means 


94  OSTEOLOGY.  fAm  % 

means  of  the  pterygoid  mufcles  ; and  that  jt  js 
for  this  reafon  we  put  between  them  any  ha^d 
body  we  wifh  to  break. 

The  canini  and  incifores  are  placed  farthc^r 
from  this  point,  and  of  eo.urfe  cannot  e;?eert  fq 
much  force  ; but  they  are  made  for  cutting  and 
tearing  the  food,  and  this  form  feems  tq  make 
amends  for  their  deficiency  in  ftrength. 

There  are  examples  of  children  who  have 
come  into  the  world  with  two,  three,  and  even 
four  teeth ; but  thefe  examples  are  very  rare  :; 
and  it  is  feldom  before  the  feventh,  eighth,  or 
ninth  month  after  birth,  that  the  incifores,  whieh 
are  the  firft  formed,  begin  to  pafs  through  the 
gum.  The  fymptoms  of  dentition,  however, 
in  confequence  of  irritation  from  the  teeth,  fre- 
quently take  place  in  the  fourth  or  fifth  month. 
About  the  twentieth  or  twenty-fourth  month, 
the  canini  and  two  molares  make  their  appear- 
ance. 

The  dangerous  fymptoms  that  fometimes  aCr 
company  dentition,  are  owing  to  the  prefllire 
of  the  teeth  on  the  gum,  which  they  irritate  fq 
as  to  excite  pain  and  inflammation,  This  irri- 
tation feems  to  occafion  a gradual  wafting  of  th:^ 
gum  at  the  part,  till  at  length  the  tooth  make$its 
appearance. 

The  fymptoms  are  more  or  lefs  alarming,  in 
proportion  to  the  refiftance  which  the  gum 
affords  to  the  teeth,  and  according  to  the  number 
of  teeth  which  may  chance  to  feek  a pafiagc  .at  the 


Part  I.  OSTEOLOGY.  95 

fame  time.  Were  they  all  to  appear  at  once, 
children  would  fall  vidims  to  the  pain  and  ex- 
ceffive  irritation  ; but  nature  has  fo  very  wifely 
difpofed  them,  that  they  ufually  appear  one  af- 
ter the  other,  with  fome  diftance  of  time  between 
each.  The  firft  incifor  that  appears  is  generally 
in  the  lower  jaw,  and  is  followed  by  one  in  the 
upper  jaw.  Sometimes  the  canini,  but  more 
commonly  one  of  the  molares,  begins  - to  pafs 
through  the  gum  firft. 

Thefe  20  teeth,  viz.  eight  incifores,  four  ca- 
nini, and  eight  molares,  are  called  temporary  or 
milk  teeth ^ becaufe  they  are  all  ftied  between  the 
age  of  feven  and  fourteen,  and  are  fucceeded  by 
what  are  called  the  permanent  or  adult  teeth. 
The  latter  are  of  a firmer  texture,  and  have 
larger  fangs. 

Thefe  adult  teeth  being  placed  in  a diftindl  fet 
of  alveoli,  the  upper  fockets  gradually  dil'appear, 
as  the  under  ones  increafe  in  fize,  till  at  length 
the  temporary,  or  upper  teeth,  having  no  longer 
any  fupport,  confequently  fall  out. 

To  thefe  20  teeth,  which  fucceed  the  tempo- 
rary ones,  1 2 others  are  afterwards  added,  viz. 
three  molares  on  each  fide  in  both  jaws  : and  in 
order  to  make  room  for  this  addition,  we  find 
that  the  jaws  gradually  lengthen  in  proportion 
to  the  growth  of  the  teeth ; fo  that  with  20  teeth, 
they  feem  to  be  as  completely  filled  as  they  are 
aftervyards  with  32.  This  is  the  reafon  why 

3 


^6  OSTEOLOGY.  Part  I. 

the  face  is  rounder  and  and  flatter  in  children  thaii 
in  adults. 

With  regard  to  the  formation  of  the  teeth,  we 
may  obferve,  that  in  a foetus  of  four  months,  the 
alveolar  procefs  appears  only  as  a flrallow  longi- 
tudinal groove,  divided  by  minute  ridges  into  a 
number  of  intermediate  depreflions ; in  each  of 
which  we  find  a fmall  pulpy  fubflance,  furround- 
ed  by  a vafcular  membrane.  This  gradually 
offifles,  and  its  lower  part  is  lengthened  out  to 
form  the  fang.  When  the  bony  part  of  the 
tooth  is  formed,  its  furface  begins  to  be  incrufl- 
ed  with  the  enamel.  How  the  latter  is  formed 
and  depofited,  we  are  not  yet  able  to  determine. 

The  rudiments  of  fome  of  the  adult  teeth  be- 
gin to  be  formed  at  a very  early  period,  for  the 
pulp  of  one  of  the  incifores  may  generally  be 
perceived  in  a foetus  of  eight  months,  and  the 
oflification  begins  in  it  foon  after  birth.  The 
firft  bicufpis  begins  to  offify  about  the  fifth  or 
fixth,  and  the  fecond  about  the  feventh  year. 
The  firff  adult  grinder  cuts  the  gum  about  the 
1 2th,  the  fecond  about  the  1 8th,  and  the  third, 
or  dens  fapientice^  ufually  between  the  20th  and 
30th  year. 

The  teeth,  like  other  bones,  are  liable  to  be 
affedfed  by  difeafe.  Their  removal  is  likewife 
the  natural  confequence  of  old  age  ; for  as  we 
advance  in  life,  the  alveoli  fill  up,  and  the  teeth, 
efpecially  the  incifores,  fall  out.  When  this  hap- 
pens. 


Part  I.  OSTEOLOGY*  97 

pens,  the  chin  projects  forward,  and  the  face  is 
much  fhortened. 

§ 4.  Of  the  Os  Hy aides,  (k) 

The  os  hyoides,  which  is  placed  at  the  root 
of  the  tongue,  was  fo  called  by  the  the  ancients 
on  account  of  its  fuppofed  refemblance  to  the 
Greek  letter  i,. 

It  will  be  necelfary  to  diftinguifh  in  it,  its  bo- 
dy, horns,  and  appendices. 

The  body,  which  is  the  middle  and  broadeft 
part  of  the  bone,  is  fo  placed  that  it  may  be  ea- 
fily  felt  at  the  fore  part  of  the  throat.  Anteri- 
orly it  is  irregularly  convex,  and  its  inner  fur- 
face  is  unequally  concave.  Its  cornua,  or  horns, 
which  are  flat  and  a little  bent,  being  much  longer 
than  the  body  part,  may  be  defcribed  as  forming 
the  fides  of  the  v.  The  appendices,  or  little 
horns,  as  they  are  called  by  M.  Winflow,  and 
fome  other  writers,  are  two  procelTes  which  rife 
up  from  the  articulations  of  the  cornua  with  the 
body,  and  are  ufually  connefted  with  the  fty- 
loid  procefs  on  each  fide  by  means  of  a liga- 
ment. 

G The 

(k)  This  bone  Is  very  feldom  preferved  with  the  fkeleton, 
and  cannot  be  included  among  the  bones  of  the  head, or  inany 
other  divifion  of  the  fkeleton.  Thomas  Bartholin  has  per- 
haps very  properly  defcribed  it  among  parts  contained  In  the 
mouth  ; but  the  generality  of  anatomical  writers  have  plac- 
ed it,  as  it  is  here,  after  the  bones  of  the  face. 


9S  OSTEOLOGY.  Part  I. 

The  ufes  of  this  bone  are  to  fupportthe  tongue, 
and  afford  attachment  to  a great  number  of  mufr 
cles  ; fome  of  which  perform  the  motions  of 
the  tongue,  while  others  ad;  on  the  larynx  and 
fauces. 

Sect.  III.  Of  the  Bones  of  the  Trunk. 

The  trunk  of  the  fkeleton  confifts  of  the 
fpine,  the  thorax,  and  the  pelvis. 

§ I.  Of  the  Spine. 

The  fpine  is  compofed  of  a great  number  of 
bones  called  vertrebcd.^  forming  a long  bony  co- 
lumn, in  figure  not  much  unlike  the  letter  f. 
This  column,  which  extends  from  the  head  to 
the  lower  part  of  the  body,  may  be  faid  to  con- 
fift  of  two  irregular  and  unequal  pyramids,  uni- 
ted to  each  other  in  that  part  of  the  loins  where 
the  laft  lumbar  vertebra  joins  the  os  facrum. 

The  vertebrae  of  the  upper  and  longeft  pyra- 
mid are  called  true  vertebrce^  in  contradiftindion 
to  thofe  of  the  lowermoft  pyramid,  which,  from 
their  being  immoveable  in  the  adult,  are 
ftyled vertebra.  It  is  upon  the  bones  of  the 
fpine  that  the  body  turns  ; and  it  is  to  this  cir- 
ciimftance  they  owe  their  name,  which  is  deriv- 
ed from  the  Latin  verb  vert  ere.,  to  turn. 

'I  he  true  vertebrae  are  divided  into  three  claffes 
of  cervfical,  dorfal,  and  lumbar  vertebrae. — The 

falfe 


Part  I.  OSTEOLOGY.  99 

falfe  vertebrse  confift  of  the  os  facrum  and  os  oc- 
cygis. 

In  each  vertebra,  as  in  other  bones,  it  will  be 
neceffary  to  remark  the  body  of  the  bone,  its  pro- 
celfes,  and  cavities. 

The  body,  which  is  convex  before,  and  con- 
cave behind,  where  it  allifts  in  forming  the  ca- 
vity of  the  fpine,  may  be  compared  to  part  of  a 
cylinder  cut  off  tranfverfely. 

Each  vertebra  affords  feven  proceffes.  The 
firft  is  at  the  back  part  of  the  vertebra,  and  from 
its  fhape  and  direction  is  named  the  fpinoiis  pro- 
cefs.  On  each  fide  of  this  are  two  others,  which, 
from  their  fituation  with  refpedl  to  the  fpine, 
are  called  trajifuerfe  procejfes.  The  four  others 
are  ftyled  oblique  or  articular  procejfes.  They 
are  much  fmaller  than  the  fpinous  or  tranfverfe 
ones.  Two  of  them  are  placed  on  the  upper, 
and  two  on  the  lower  part  of  each  vertebra,  ri- 
fmg  from  near  the  bafis  of  each  tranfverfe  pro- 
eefs.  They  have  gotten  the  name  of  oblique pro- 
cejfes^  from  their  fituation  with  refped;  to  the 
proceffes  with  which  they  are  articulated  ; and 
they  are  fometimes  ftyled  articular  procejfes . from 
the  manner  in  which  they  are  articulated  Vv^ith 
each  other ; the  two  fuperior  proceffes  of  one 
vertebra  being  articulated  with  the  two  other  in- 
ferior proceffes  of  the  vertebra  above  it.  Each 
of  thefe  proceffes  is  covered  with  cartilage  at  its 
articulation,  and  their  articulations  with  each 
other  are  by  a fpecies  of  ginglimua. 

G 2 


In 


lOO 


OSTEOLOGY.  Part  I. 

In  each  vertebra,  between  its  body  and  its 
proceffes,  we  find  a hole  large  enough  to  admit 
a finger.  Thefe  holes  or  foramina,  correfpond 
with  each  other  through  all  the  vertebrse,  and 
form  the  long  bony  channel  in  which  the  fpinal 
marrow  is  placed.  We  may  likewife  obferve 
four  notches  in  each  vertebra.  Two  of  thefe 
notches  are  at  the  upper,  and  two  at  the  lower 
part  of  the  bone,  between  the  oblique  procefles 
and  the  body  of  the  vertebra.  Each  of  thofe 
notches  meeting  with  a fimilar  opening  in  the 
vertebra  above  or  below  it,  forms  a foramen  for 
the  paflage  of  blood-veflels,  and  of  the  nerves 
out  of  die  fpine. 

The  bones  of  the" fpine  are  united  together  by 
means  of  a fubftance,  which  in  young  fubjedts 
appears  to  be  of  a ligamentous,  but  in  adults 
more  of  a cartilaginous  nature.  This  interver- 
tebral fubftance,  which  forms  a kind  of  partition 
betw'een  the  feveral  vertebrae,  is  thicker  and  more 
flexible  between  the  lumbar  vertebrae  than  in  the 
other  parts  of  the;  fpine,  the  moft  confiderable 
motions  of  the  triuik  being  performed  on  thofe 
vertebrae.  This  fubftance  being  very  elaftic, 
the  extenlion  and  flexion  of  the  body,  and  its 
motion  backwards  and  forwards,  or  to  either  fide, 
are  performed  with  great  facility.  This  elafti- 
city  feems  to  be  the  reafon  why  people  who  have 
been  long  ftanding,  or  have  carried  a confidera- 
ble weight,  are  found  to  be  fhorter  than  when 
they  have  been  long  in  bed.  In  the  two  firft 

inftances 


101 


Part  I.  OSTEOIOGY. 
inftances  the  intervertebral  cartilages  (as  they  are 
ufually  called)  are  evidently  more  expofed  to 
compreffion  than  when  we  are  in  bed  in  an  ho- 
rizontal pofture. 

In  advanced  life  thefe  cartilages  become  fhri- 
velled,  and  of  courfe  lofe  much  of  their  elafti- 
city.  This  may  ferve  to  account  for  the  decreafe 
in  ftature  and  the  ftooping  forward  which  are 
ufually  to  be  obferved  in  old  people. 

Befides  the  connection  of  the  feveral  vertebrse 
by  means  of  this  intervertebral  fubftance,  there 
are  likewife  many  ftrong  ligaments,  both  exter- 
nal and  internal,  which  unite  the  bones  of  the 
fpine  to  each  other.  Their  union  is  alfo  ftrength- 
ed  by  a variety  of  ftrong  mufcles  that  cover  and 
furround  the  fpine. 

The  bones  of  the  fpine  are  found  to  diminifti 
in  denfity,  and  to  be  lefs  firm  in  their  texture  in 
proportion  as  they  increafe  in  bulk  ; fo  that  the 
lowermoft  veitebrse,  though  the  largeft,  are  not 
fo  heavy  in  proportion  as  the  upper  ones.  By 
this  means  the  fize  of  thefe  bones  is  increafed 
without  adding  to  their  weight ; a circumftance 
of  no  little  importance  in  a part  like  the  fpine, 
which,  befides  flexibility  and  fupplenefs,  feems 
to  require  lightnefs  as  one  of  its  eflential  proper- 
ties. 

In  very  young  chiidaien,  each  veterbra  con- 
fifts  of  three- bony  pidces  united  by  cartilages 
which  afterwards  olfify. 

There  are  feven  vertebra  of  the  neck — they 

are 


102  OSTEOLOGY.  Part  I. 

are  of  a firmer  texture  than  the  other  bones  of 
the  fpine.  Their  tranfverfe  procelTes  are  forked 
for  the  lodgement  of  mufcles,  and  at  the  bottom  of 
each  we  obferve  a foramen,  through  which  pafs 
the  cervical  artery  and  vein.  The  firft  and  fe- 
cond  of  thefe  vertebrse  muft  be  defcribed  more 
par'  iculaiiy.  The  firft  approaches  almoft  to  an 
c al  lhape — On  its  fuperior  furface  it  has  two 
cities  which  admit  the  condyles  of  the  occipi- 
ai  bone  with  which  it  is  articulated.  This  ver- 
ebra,  which  is  called  atlas  from  its  fupporting 
the  head,  cannot  well  be  defcribed  as  having 
either  body  or  fpinous  procefs,  being  a kind  of 
bony  ring.  Anteriorly,  where  it  is  articulated 
to  the  odontoid  procefs  of  the  fecond  vertebra, 
it  is  very  thin.  On  its  upper  furface  it  has  two 
cavities  which  admit  the  condyles  of  the  occipi- 
tal bone.  By  this  connexion  the  head  is  allow- 
ed to  move  forwards  and  backwards,  but  has  very 
little  motion  in  any  other  direction. 

The  fecond  vertebra  has  gotten  the  name  of 
dentata^  from  its  having,  at  its  upper  and  anterior 
part,  a procefs  called  the  odontoid  or  tooth-like 
procefs^  which  is  articulated  with  the  atlas,  to 
which  this  fecond  vertebra  may  be  faid  to  ferve  as 
an  axis.  This  odontoid  procefs  is  of  a cylindri- 
cal fhape,  fomewhat  flattened,  however,  ante- 
riorly and  pofteriorly.  At  its  fore-part  where 
it  is  received  by  the  atlas,  we  may  obferve  a 
fmooth,  convex,  articulating  furface.  It  is  by 
means  of  this  articulation  that  the  head  performs 

ks 


Part  I.  OSTEOLOGY.  103 

its  rotatory  motion,  the  atlas  in  that  cafe  moving 
upon  this  odontoid  procefs  as  upon  a pivot.  But 
when  this  motion  is  in  any  confiderable  degree, 
or,  in  other  words,  when  the  head  moves  much 
either  to  the  right  or  left,  all  the  cervical  verte- 
brse  feem  to  affift,  otherwife  the  fpinal  m.arrow 
would  be  in  danger  of  being  divided  tranfverfe- 
ly  by  the  firft  vertebra. 

Vertebra  of  the  back.  The  fpinous  procefs  of 
each  of  the  cervical  vertebrse  is  fhorter,  and  their 
articular  procelfes  more  oblique,  than  in  the  other 
bones  of  the  fpine. 

Thefe  12  vertebr;^  are  of  a middle  fize  be- 
tween thofe  of  the  neck  and  loins.  At  their 
fides  we  may  obferve  two  depreffions,  one  at  the 
upper  and  the  other  at  the  lower  part  of  the  bo- 
dy of  each  vertebra  ; which  uniting  with  fimi- 
lar  depreffions  in  the  vertebrae  above  and  below, 
form  articulating  furfaces,  covered  with  cartilages 
for  receiving  the  heads  of  the  ribs  ; and  at  the 
fore-part  of  their  tranfverfe  procefs  (excepting 
the  two  laft)  we  find  an  articulating  furface  for 
receiving  the  tuberofity  of  the  ribs. 

Lumbar  vertebra.  Thefe  five  vertebrae  differ 
only  from  thofe  of  the  back  in  their  being  larger, 
and  in  having  their  fpinous  proceffes  at  a greater 
diftance  from  each  other.  The  moft  confider- 
able motions  of  the  trunk  are  made  on  thefe 
vertebrae  ; and  thefe  motions  could  not  be  per- 
formed with  fo  much  eafe,  were  the  proceffes 
placed  nearer  to  each  other. 


The 


104  OSTEOLOGY.  Part  L 

The  os  SACRUM  which  is  compofed  of  five 
or  fix  pieces  in  young  fubjedfs,  becomes  one 
bone  in  more  advanced  age. 

It  is  nearly  of  a triangular  figure,  its  inferior 
portion  being  bent  a little  forwards.  Its  fuperior 
part  has  two  oblique  procefl'es  which  are  articu^ 
lated  with  the  laft  of  the  lumbar  vertebrse  ; and_ 
it  has  likewife  commonly  three  fmall  fpinous 
proceffes,  which  gradually  become  fhorter,  fo 
that  the  lowermoft  is  not  fo  long  as  the  fecond, 
nor  the  fecond  as  the  uppermoft.  Its  tranfverfe 
proceffes  are  formed  into  one  oblong  procefs, 
which  becomes  gradually  fmaller  as  it  defcends. 
Its  concave  or  anterior  fide  is  ufually  fmooth,  but 
its  pofterior  convex  fide  has  many  prominences 
(the  moft  remarkable  of  which  are  the  fpinous 
proceffes  juft  now  mentioned),  which  are  filled 
up  and  covered  with  the  mufcular  and  tendinous 
parts  behind, 

This  bone  has  five  pair  of  holes,  which  af- 
ford a paffage  to  blood-veffels,  and  likewife  to 
the  nerves  that  are  derived  from  the  fpinal 
marrow,  which  is  continued  even  here,  being 
lodged  in  a triangular  cavity,  that  becomes  fmaller 
as  it  defcends,  and  at  length  terminates  oblique-r 
ly  at  the  lowey  part  of  this  bone.  Below  the 
third  divifion  of  the  os  facrum,  this  canal  is  not 
completely  bony  as  in  the  reft  of  the  fpine,  be- 
ing fecured  as  its  back  part  only  by  a very  ftrong 
membrane,  fo  that  a wound  at  this  part  muft  be 
extremely  dangerous. 

The 


Part  I.  OSTEOLOGY.  105 

, The  os  facrum  is  united  laterally  to  the  olTa 
Innominata  or  hip-bones,  and  belov/  to  the" 
coccyx. 

Os  Coccyx.  The  coccyx,  which,  like  the  os 
facrum,  is  in  young  people  made  up  of  three 
or  four  diftindt  parts,  ufually  becomes  one  bone 
in  the  adult  ftate. 

It  ferves  to  fupport  the  inteftinum  redlum ; and, 
by  its  being  capable  of  fome  degree  of  motion 
at  its  articulation  with  the  facrum,  and  being 
like  that  bone  bent  forwards,  we  are  enabled  to 
fit  with  eafe. 

This  bone  is  nearly  of  a triangular  fhape,  be- 
ing broadeft  at  its  upper  part,  and  from  thence 
growing  narower  to  its  apex,  where  it  is  not 
bigger  than  the  little  finger. 

It  has  got  its  name  from  its  fuppofed  refem- 
blance  a cuckow’s  beak.  It  differs  greatly  from 
the  vertebrae,  being  commonly  without  any  pro- 
ceffes,  and  having  no  cavity  for  the  fpinal  mar- 
row, or  foramina  for  the  tranfmiflion  of  nerves. 

The  fpine,  of  which  we  have  now  finifhed 
the  anatomical  defcription,  is  deftined  for  many 
great  and  important  ufes.  The  medulla  fpinalis 
is  lodged  in  its  bony  canal  fecure  from  external 
injury.  It  ferves  as  a defence  to  the  abdominal 
and  thoracic  vifcera,  and  at  the  fame  time  fup- 
ports  the  head,  and  gives  a general  firmnefs  to 
the  whole  trunk. 

We  have  before  compared  it  to  the  letteryj  and 
its  different  turns  will  be  found  to  render  it  not 

very 


io6  OSTEOLOGY.  Part  L 

Very  unlike  the  figure  of  that  letter. — In  the  neck 
“vve  fee  it  projecting  fomewhat  forward  to  fupport 
the  head,  which  without  this  affiftance  would 
require  a great  number  of  mufcles. — Lower 
down,  in  the  thorax,  we  find  it  taking  a curved 
direction  backwards,  and  of  courfe  increafing 
the  cavity  of  the  cheft.  After  this,  in  the  loins, 
it  again  projects  forwards  in  a direction  with  the 
centre  of  gravity,  by  which  means  we  are  eafi-^ 
ly  enabled  to  keep  the  body  in  an  ereCt  pofture, 
for  otherwife  we  fhould  be  liable  to  fall  forward. 
Towards  its  inferior  extremity,  however,  it 
again  recedes  backward,  and  thus  aflifts  in  form-r 
ing  the  pelvis,  the  name  given  to  the  cavity  in 
which  the  urinary  bladder,  inteftinum  reCtum, 
and  other  vifcera  are  placed. 

If  this  bony  column  had  been  formed  only  of 
one  piece,  it  would  have  been  much  more  eafi-* 
ly  fractured  than  it  is  now  : and  by  confining  the 
trunk  to  a ftiff  fituation,  a variety  of  motions 
would  have  been  altogether  prevented,  which 
are  now  performed  with  eafe  by  the  great  num- 
ber of  bones  of  which  it  is  compofed. 

It  is  firm,  and  yet  to  this  firmnefs  there  is 
added  a perfeCt  flexibility.  • If  it  be  required  to 
carry  a load  upon  the  head,  the  neck  becomes 
ftiff  with  the  affiftance  of  its  mufcles,  and  ac- 
commodates itfelf  to  the  load,  as  if  it  was  com- 
pofed only  of  one  bone — In  ftooping  likewife, 
or  turning  to  either  fide,  the  fpine  turns  in  itfelf 

every 


Part  I.  OSTEOLOGY.  107 

every  direction,  as  if  all  its  bones  were  feparated 
from  each  other. 

In  a part  of  the  body  like  the  fpine,  that  is 
made  up  of  fo  great  number  of  bones,  and  in- 
tended for  fuch  a variety  of  motion,  there  muft 
be  a greater  danger  of  diflocation  than  fracture  ; 
but  we  fhall  find,  that  is  very  wifely  guarded 
againft  in  every  direction  by  the  procelTes  belong- 
ing to  each  vertebra,  and  by  the  ligaments,  car- 
tilages, &c.  by  which  thefe  bones  are  conned- 
ed  with  each  other. 

§ 2.  Of  the  Bones  of  the  I’horax. 

The  thorax,  or  cheft,  is  compofed  of  many 
bones,  viz.  the  fternum  which  is  placed  at  its  an- 
terior part,  twelve  ribs  on  each  fide  which  make 
up  its  lateral  parts,  and  the  dorfal  vertebrse  which 
conftitute  its  pofterior  part.  Thefe  laft  have  been 
already  defcribed. 

The  fernum  is  the  long  bone  which  extends 
itfelf  from  the  upper  to  the  lower  part  of  the 
breaft  anteriorly,  and  to  which  the  ribs  and  the 
clavicles  are  articulated. 

In  children  it  is  cqmpofed  of  feveral  bones 
united  by  cartilages  ; but  as  we  advance  in  life, 
moft  of  thefe  cartilages  oflify,  and  the  flernum 
in  the  adult  ftate  is  found  to  confift  only  of  three 
pieces,  and  fometimes  become  one  bone.  It  is 
however  generally  defcribed  as  being  compofed 
of  three  parts — one  fuperior,  which  is  broad, 

thick, 


ro8  OSTEOLOGY.  Part  I. 

thick,  and  fhort ; and  one  in  the  middle,  which 
is  thinner,  narrower,  and  longer  than  the  other. 

It  terminates  at  its  lower  part  by  a third  piece, ' 
which  is  called  the  xyphoid^  ox fword-Uke  carti-r 
lage^  from  its  fuppofed  refemblance  to  the  blade 
of  a fword,  and  becaufe  in  young  fubjedts  it  is 'I 
commonly  in  a cartilaginous  ftate. 

We  have  already  obferved,  that  this  bone  is 
articulated  with  the  clavicle  on  each  fide.  It  is  , 
likewife  joined  to  the  fourteen  true  ribs,  viz. 
feven  on  its  right  and  feven  on  its  left  fide. 

The  rtbs  are  bones  fhaped  like  a bow,  form- 
ing the  fides  of  the  cheft.  There  are  twelve  on  J 
each  fide.  They  are  diftinguifhed  into  true  andil 
falfe  ribs ; the  feven  upper  ribs  which  are  arti- 
culated to  the  fternum  are  called  true  ribs^  and 
the  five  lower  ones  that  are  not  immediately  at- 
tached to  that  bone  are  called  falfe  ribs. 

,j  On  the  inferior  and  interior  furface  of  each  rib,.) 
we  obferve  a finuofity  for  the  lodgement  of  an 
artery,  vein,  and  nerve. 

The  ribs  are  not  bony  through  their  whole 
length,  their  anterior  part  being  cartilaginous*): 
They  are  articulated  with  the  vertebrae  aiid  fter-  ' 
num.  Every  rib  (or  at  leaft  the  greater  num- 
ber of  them)  has  at  its  pofterior  part  two  pro- 
celfes ; one  at  its  extremity  called  the  head  of 
the  rib,  by  meanss  of  which  it  is  articulated  with 
the  body  of  two  vertebrae  ; and  another,  call- 
ed its  tuberofity,  by  which  it  is  articulated  with 
the  tranfverfe  procefs  of  the  loweft  of  thefe  two 

vertebrae. 


PartL  osteology.  109 

vertebrae.  The  firft  rib  is  not  articulated  by  its 
extremity  to  two  vertebrae,  being  fimply  attach- 
• ^ ed  to  the  upper  part  of  the  firft  vertebra  of  the 
back.  , The  feven  fuperior  or  true  ribs  are  arti- 
culated anteriorly  with  the  fternum  by  their  car- 
tilages ; but  the  falfe  ribs  are  fupported  in  a dif- 
ferent manner — the  eighth,  which  is  the  firft  of 
thefe  fibs,  being  attached  by  its  cartilages  to  the 
feventh  ; the  ninth  to  the  eighth,  &c. 

The  two  lowermoft  ribs  differ  likewife  from 
all  the  reft  in  the  following  particulars  : They  are 
articulated  only  with  the  body  of  the  vertebra, 
and  not  with  a tranfverfe  procefs  ; and  anterior- 
ly, their  cartilage  is  loofe,  not  being  attached 
to  the  cartilages  of  the  other  ribs ; and  this  feems 
to  be,  becaufe  the  moft  confiderable  motions  of 
!the  trunk  are  not  performed  on  the  lumbar  verte- 
brae alone,  but  likewife  on  the  two  laft  vertebrae 
ilii  of  the  back  ; fo  that  if  thefe  two  ribs  had  been 
an  confined  at  the  fore  part  like  the  other  ribs,  and 
had  been  likewife  articulated  with  the  bodies  of 
:-two  vertebrae,  and  with  the  tranfverfe  proceffes, 
the  motion  of  the  two  laft  vertebrae,  and  con- 
fequently  of  the  whole  trunk,  would  have  been 
impeded. 

The  ribs  help  to  form  the  cavity  of  the 
; thorax  ; they  afford  attachment  to  different 
mufcles  ; they  are  ufeful  in  refpiration  ; and 
they  ferve  as  a fecurity  to  the  heart  and  lungs. 


ffi. 


§3-  Of 


no 


OSTEOLOGY. 


Part  L 


§ 3*  Bones  of  the  Pelvis. 

The  pelvis  is  compofed  of  the  os  facrum,  os 
coccygis,  and  two  offa  innomiriata.  The  tvsro 
jfirft  of  thefe  bones  w^ere  included  in  the  account  i 
of  the  fpine,  to  which  they  more  properly  be- 
long. 

In  children,  each  os  innominatum  is  compof- 
ed of  three  diftindt  bones  ; but  as  we  advance  in 
life  the  intermediate  cartilages  gradually  offify, 
and  the  marks  of  the  original  feparation  difap- 
pear,  fo  that  they  become  one  irregular  bone ; 
ftill  however  continuing  to  retain  the  names  of 
ilium,  ifchium,  and  pubis,  by  which  their  divi- 
fions  were  originally  diftinguifhed,  and  to  be  de- 
fcribed  as  three  different  bones  by  the  generality 
of  anatomifts.  The  os  ilium  forms  the  upper 
and  moft  confiderable  part  of  the  bone,  the  os 
ifchium  its  lower  and  pofterior  portion,  and  the 
os  pubis  its  fore  part. 

The  os  ilium  or  haunch  bone,  is  articulated 
pofteriorly  to  the  os  facrum  by  a firm  cartilagin- 
ous fubftance,  and  is  united  to  the  os  pubis  be- 
fore and  to  the  os  ifchium  below.  Its  faperior 
portion  is  thin,  and  terminates  in  a ridge  called 
the  crifta  or  fpine  of  the  ilium,  and  more  com- 
monly known  by  the  name  of  the  haunch.  This 
crilfa  rifes  up  like  an  arch  ; being  turned  fome- 
what  outwards,  fo  as  to  refemble  the  wings  of  a | 
phaeton. 

Externally  this  bone  is  unequally  prominent  i 

and  ; 


1 1 1 


Part  I.  OSTEOLOGY, 
and  hollowed  for  the  lodgement  of  mufcles  ; in- 
ternally we  find  it  fmooth  and  concave.  At  its 
lower  part  there  is  a confiderable  ridge  on  its  in- 
ner furface.  This  ridge  extends  from  the  os  fa- 
crum,  and  correfponds  v/ith  a fimilar  prominence 
both  on  that  bone  and  the  ifchium  ; forms  with 
the  inner  part  of  the  offa  pubis  what  in  midwifery 
is  termed  the  brim  of  the  pelvis. 

The  crifta,  or  fpine,  which  at  firft  is  an  epi- 
phyfis,  has  two  confiderable  tuberofities ; one 
anteriorly,  and  the  other  pofteriorly,  which  is 
the  largeft  of  the  two  : Thefe,  from  their  pro- 
jecting more  than  the  parts  of  the  bone  below 
them,  have  gotten  the  name  of  fpinal  procefTes. 
From  the  anterior  fpinous  procefs,  the  fartorius 
and  tenfor  vagina  femoris  mufcles  have  their  ori- 
gin ; and  below  the  pofterior  procefs  we  obferve 
a confiderable  niche  in  the  bone,  which,  in  the 
recent  fubjeCt,  is  formed  into  a large  foramen, 
by  means  of  a ftrong  ligament  that  is  ftretched 
over  its  lower  part  from  the  os  facrum  to  the 
fharp-pointed  procefs  of  the  ifchium.  This 
hole  affords  a paffage  to  the  great  fciatic  nerve, 
and  to  the  pofferior  crural  veffels  under  the  py- 
riform mufcle,  part  of  which  likewife  paffes  out 
here. 

The  os  ifchium^  or  hip-bone,  which  is  of  a very 
irregular  figure,  conflitutes  the  lower  lateral  parts 
of  the  pelvis,  and  is  commonly  divided  into  its 
body,  tuberofity,  and  ramus.  The  body  forms 
the  lower  and  moft  confiderable  portion  of  the 

acetabulum, 


1 12 


OSTEOLOGY.  Part  1 
acetabulum,  and  fends  a fharp-pointed  procefs 
backwards,  called  the  fpine  of  the  ifchiiim.  To 
this  procefs  the  ligament  adheres,  which  was  juft 
now  fpoken  of,  as  forming  a foramen  for  the 
paffage  of  the  fciatic  nerve. — T he  tuberofity,' 
which  is  the  loweft  part  of  the  trunk,  and  fup- 
ports  us  when  we  fit,  is  large  and  irregular,  af- 
fording origin  to  feveral  mufcles.  From  this  tu- 
berofity we  find  the  bone  becoming  thinner  and 
narrower.  This  part,  which  has  the  name  of 
ramus  or  branch,  paffes  forwards  and  upwards, 
and  concurs  with  the  ramus  of  the  os  pubis,  to 
form  a large  hole  called  the  foramen  magnum 
ifchli^  or  thyroideiim^  as  it  is  fometimes  named, 
from  its  refemblance  to  a door  or  fhield.  This 
hole,  which  in  the  recent  fubjedt  is  clofed  by  a 
ftrong  membrane  called  the  obturator  ligament, 
affords  through  its  whole  circumference  attach- 
ment to  mufcles.  At  its  upper  part  where  we 
obferve  a niche  in  the  bone,  it  gives  paffage  to 
the  obturator  veffels  and  nerves,  which  go  to  the 
inner  part  of  the  thigh.  Nature  feems  every 
where  to  avoid  an  unneceffary  weight  of  bone, 
and  this  foramen,  no  doubt,  ferves  to  lighten  the 
bones  of  the  pelvis. 

The  os  pubis ^ or  fhare-bone,  which  with  its 
fellow  forms  the  fore-part  of  the  pelvis,  is  the 
fmalleft  divifion  of  the  os  innominatum.  It  is 
united  to  its  fellow  by  means  of  a ftrong  car- 
tilage, which  forms  what  is  called  the  fymphyfis 
pubis. 


3 


In 


Part  I.  OSTEOLOGT.  iij 

In  each  os  pubis  we  may  diilinguifh  the  body 
of  the  bone,  its  angle,  and  ramus.  The  body 
or  outer  part  is  united  to  the  os  ilium.  The  angle 
comes  forward  to  form  the  fymphyfis,  and  the 
ramus  is  a thin  procefs  which  unites  with  the 
ramus  of  the  ifchium,  to  form  the  foramen  thy- 
roideum. 

The  three^bones  we  have  defcribed  as  compof- 
ing  each  os  innominatum,  all  affift  in  forming 
the  acetabulum,  in  which  the  head  of  the  os 
femoris  is  received. 

This  cavity  is  every  where  lined  withafmooth 
cartilage,  excepting  at  its  inner  part,  where  we 
may  obferve  a little  folTa,  in  which  are  lodged 
the  mucilaginous  glands  of  the  joint.  We  may 
likewife  notice  the  pit  or  depreffion  made  by  the 
round  ligament,  as  it  is  improperly  called,  which, 
by  adhering  to  this  cavity  and  to  the  head  of 
the  thigh-bone,  helps  to  feeure  the  latter  in  the 
focket. 

Thefe  bones,  which  are  united  to  each  other 
and  to  the  fpine  by  many  very  ftrong  ligaments, 
ferve  to  fupport  the  trunk,  and  to  conneft  it  with 
the  lower  extremities ; and  at  the  fame  time  to 
form  the  pelvis  or  bafon,  in  which  are  lodg- 
ed the  inteftines  and  urinary  bladder,  and  in 
women  the  uterus  ; fo  that  the  ftudy  of  this  part 
of  ofteology  is  of  the  utmoft  importance  in  mid- 
wifery. 

It  is  worthy  of  obfervation,  that  in  women 
the  os  facrum  is  ufually  fhorter,  broader,  and 

H more 


II4  OSTEOLOGY.  Part  I. 

more  hollowed,  the  offa  ilia  more  expanded, 
and  the  inferior  opening  of  the  pelvis  larger  than 
in  men. 

Sect.  IV.  Of  the  ^Extremities. 

These  parts  of  the  fkeleton  confift  of  the  up- 
per extremity  and  the  lower. 

% Of  the  Upper  Extremity. 

This  confifts  of  the  fhoulder,  the  arm,  and 
the  hand. 

I.  Of  the  Shoulder. 

The  fhoulder  confifts  of  two  bones,  the  cla- 
vicula  and  the  fcapula. 

The  former,  which  is  fo  named  from  its  re- 
femblance  to  the  key  in  ufe  amongft  the  ancients, 
is  a little,  curved  at  both  its  extremities  like  an 
italic  f.  It  is  likewife  called  jugulum^  or  collar- 
bone, from  its  fituation.  It  is  about  the  fize  of 
the  little  finger,  but  longer,  and  being  of  a very 
fpongy  fubftance  is  very  liable  to  be  fractured.  In 
this,  as  in  other  long  bones,  we  may  diftinguifli 
a body  and  two  extremities.  The  body  is  rather 
flattened  than  rounded.  The  anterior  extremity 
is  formed  into  a llightly  convex  head,  which  is 
nearly  of  a triangular  ftiape.  The  inferior  fur- 
face  of  the  head  is  articulated  with  the  fternum. 
The  pofterior  extremity,  which  is  flatter  and 
broader  than  the  other,  is  connected  to  a pro- 
cefs  of  the  fcapula,  called  acromion.  Both 

thefe 


Part  I.  OSTEOLOGY.  115 

thefe  articulations  are  fecured  by  ligaments,  and 
in  that  with  the  fternuin  we  meet  with  a move- 
able  cartilage,  to  prevent  any  injury  from  fric- 
tion. 

The  clavicle  ferves  to  regulate  the  motions  of 
the  fcapula,  by  preventing  it  from  being  brought 
too  much  forwards,  or  carried  too  far  back- 
wards. It  affords  origin  to  feveral  mufcles,  and 
helps  to  cover  and  protect  the  fubclavian  veffels, 
which  derive  their  name  from  their  fituation  un- 
der this  bone. 

The  fcapula^  or  fhoulder-blade,  which  is  near- 
ly of  a triangular  fhape,  is  fixed  to  the  pofterior 
part  of  the  true  ribs,  fomewhat  in  the  manner 
of  a buckler.  It  is  of  a very  unequal  thicknefs, 
and,  like  all  other  broad,  flat  bones,  is  fomewhat 
cellular.  Exteriorly  it  is  convex,  and  interiorly 
concave,  to  accommodate  itfelf  to  the  convexity 
of  the  ribs.  We  obferve  in  this  bone  three  un- 
equal fides,  which  are  thicker  and  fironger  than 
the  body  of  the  bone,  and  are  therefore  termed 
its  cojia.  The  largeft  of  the  three,  called  alfo 
the  bafis,  is  turned  towards  the  vertebrae.  An- 
other, which  is  lefs  than  the  former,  is  below 
this ; and  the  third,  which  is  the  leaft  of  the 
three,  is  at  the  upper  part  of  the  bone.  Exter- 
nally the  bone  is  elevated  into  a confiderable  fpine, 
which  rifmgTmali  at  the  bafis  of  the  fcapula,  be- 
comes gradually  higher  and  broader,  and  divides 
the  outer  furface  of  the  bone  into  two  foiTse. 

H 2 The 


ii6  OSTEOLOGY.  Part  I, 

The  ruperior  of  thefe,  which  is  the  fmalleft,  ferves 
to  lodge  the  fupra  fpinatiis  mufcle  ; and  the  in- 
ferior folfa,  which  is  much  larger  than  the  other, 
gives  origin  to  the  infra  fpinatus.  This  fpine 
terminates  in  a broad  and  flat  procefs  at  the  top 
of  the  Ihoulder,  called  the  pj~oceJfus  acromion^  to 
which  the  clavicle  is  articulated.  This  procefs  is 
hollowed  at  its  lower  part  to  allow  a paflfage  to 
the  fupra  and  infra  fpinati  mufcles.  The  fcapula 
has  likewife  another  conliderable  procefs  at  its 
upper  part,  which,  from  its  refemblance  to  the 
beak  of  a bird,  is  called  the  coracoid  procefs.  From 
the  outer  fide  of  this  coracoid  procefs,  a ftrong 
ligament  palfes  to  the  proceflTus  acromion,  v/hich 
prevents  a luxation  of  the  os  humeri  upwards. 
A third  procefs  begins  by  a narrow  neck,  and 
ends  in  a cavity  called  glenoid.,  for  the  conne<ff  ion 
of  the  os  humeri. 

The  fcapula  is  articulated  with  the  clavicle  and 
os  humeri,  to  which  lafl;  it  fer^'es  as  a fulcrum  ; 
and  by  varying  its  pofition  it  affords  a greater 
fcope  to  the  bones  of  the  arm  in  their  different 
motions.  It  likewife  gives  origin  to  feveral 
mufcles,  and  pofteriorly  ferves  as  a defence  to 
the  trunk. 

2.  Bones  of  the  Arm. 

The  arm  is  commonly  divided  into  two  parts, 
which  are  articulated  to  each  other  at  the  elbow. 
The  upper  part  retains  the  name  of  arm,  proper^ 

ly 


Part  I.  OSTEOLOGY.  117 

ly  fo  called,  and  the  lower  part  is  ufually  called 
the  fore  arm. 

The  arm  is  compofed  of  a fmgle  bone  called 
os  humeri.  This  bone,  which  is  almoft  of  a cy- 
lindrical fhape,  may  be  divided  into  its  body  and 
its  extremities. 

The  upper  extremity  begins  by  a large,  round 
fmooth  head,  which  is  admitted  into  the  glenoid 
cavity  of  the  fcapula.  On  the  upper  and  fore 
part  of  the  bone  there  is  a groove  for  lodging  the 
long  head  of  the  biceps  mufcle  of  the  arm  ; and 
on  each  fide  of  the  groove,  at  the  upper  end  of  the 
bone,  there  is  a tubercle  to  which  the  fpinata 
mufcles  are  fixed. 

The  lower  extremity  has  feveral  proceffes  and 
cavities.  The  principal  proceffes  are  its  two  con- 
dyles, one  exterior  and  the  other  interior,  and 
of  thefe  the  laft  is  the  largeft.  Between  thefe 
two  we  obferve  two  lateral  protuberances,  which, 
together  with  a middle  cavity,  form  as  it  were  a 
kind  of  pully  upon  which  the  motions  of  the 
fore-arm  are  chiefly  performed.  At  each  fide 
of  the  condyles,  as  well  exteriorly  as  interiorly, 
there  is  another  eminence  which  gives  origin  to 
feveral  mufcles  of  the  hand  and  fingers.  Pofte- 
riorly  and  fuperiorly,  fpeaking  with  refpedt  to 
the  condyles,  we  obferve  a deep  foffa  which  re- 
ceives a confiderable  procefs  of  the  ulna : and 
anteriorly  and  oppofite  to  this  foffa,  we  obferve 
another,  which  is  much  lefs  and  receives  another 
procefs  of  the  fame  bone. 


The 


ii8  OSTEOLOGY.  Part  I. 

The  body  of  the  bone  has  at  its  upper  and 
and  anterior  part  a furrow  which  begins  from  be- 
hind the  head  of  the  bone,  and  ferves  to  lodge 
the  tendon  of  a mufcie.  The  body  of  the  os 
humeri  is  hollow  through  its  whole  length,  and, 
like  all  other  long  bones,  has  its  marrow. 

Tills  bone  is  articulated  at  its  upper  part  to  the 
fcapula.  This  articulation,  which  allows  motion 
every  way,  is  fiirrounded  by  a capfular  ligament; 
tliat  is  fometim.es  torn  in  luxation,  and  becomes 
an  obftacle  to  the  eafy  redudtion  of  the  bone. 
Its  lower  extremity  is  articulated  with  the  bones 
of  the  fore-arm. 

The  fore-arm  is  compofed  of  two  bones,  the 
ulna  and  radius. 

The  ulna  or  elbow-bone  is  much  Icfs  than  the 
os  humeri,  and  becomes  gradually  fmaller  as  it 
defcends  to  the  wrift.  At  is  upper  part  it  has 
two  procefles  and  two  cavities.  Of  the  two  pro- 
cefles,  the  largeft,  which  is  fituated  pofleriorly, 
and  called  the  olecranon^  is  admitted  into  the  pof- 
terior  foffa  of  the  os  humeri.  The  other  procefs 
is  placed  anteriorly,  and  is  called  the  coronoid pro- 
cefs. In  bending  the  arm  it  enters  into  the  ante- 
rior foffa  of  the  os  humeri.  This  procefs  being 
much  fmaller  than  the  other,  permits  the  fore- 
arm to  bend  inwards  ; whereas  the  olecranon, 
which  is  fhaped  like  a hook,  reaches  the  bottom 
cf  its  foffa  in  the  os  humeri  as  foon  as  the  arm 
becomes  ftraight,  and  will  not  permit  the  fore-arm 

tcv^ 


PartL  osteology.  119 

to  be  bent  backwards.  The  ligaments  llkewife 
oppofe  this  motion. 

Between  the  two  proceffes  we  have  defcribed^ 
there  is  a conhderable  cavity  called  the  fygmoid 
cavity,  divided  into  two  folfe  by  a fmall  eminence, 
which  paffes  from  one  procefs  to  the  other ; it  is 
by  means  of  this  cavity  and  the  two  proceffes, 
that  the  ulna  is  articulated  with  the  os  humeri  by 
ginglimus.  ^ 

At  the  bottom  of  the  coronoid  procefs  inte- 
riorly, there  is  a fmall  fygmoid  cavity,  which 
ferves  for  the  articulation  of  the  ulna  with  the 
radius. 

The  body  of  the  ulna  is  of  a triangular  lhape  ; 
Its  lower  extremity  terminates  by  a fmall  head 
and  a little  ftyloid  procefs.  The  ulna  is  articu- 
lated above  to  the  os  humeri — both  above  and 
below  to  the  radius,  and  to  the  wrift  at  its  lower 
extremity.  All  thefe  articulations  are  fecm'ed  by 
means  of  ligaments.  The  chief  ufe  of  this  bone 
feems  to  be  to  fupport  and  regulate  the  motions 
of  the  radius. 

The  radius^  which  is  fo  named  from  its  fup- 
pofed  refemblance  to  the  fpoke  of  a wheel,  is 
placed  at  the  infide  of  the  fore-arm.  It  is  fome- 
what  larger  than  the  ulna,  but  not  quite  fo  long 
as  that  bone.  Its  upper  part  is  cylindrical,  hol- 
lowed fuperiorly  to  receive  the  outer  condyle  of 
the  os  humeri.  Laterally  it  is  admitted  into  the 
little  fygmoid  cavity  of  the  ulna,  and  the  cylin- 
drical part  of  the  bone  turns  in  this  cavity  in  the 

motions 


220 


OSTEOLOGY.  Part  I. 
motions  of  pronation  and  fupination  (i).  This 
bone  follows  the  ulna  in  flexion  and  extenfion, 
and  may  likewife  be  moved  round  its  axis  in  any 
direction.  The  lower  extremity  of  the  radius 
is  much  larger  and  ftronger  than  its  upper  part ; 
the  ulna,  on  the  contrary,  is  fmaller  and  weak- 
er below  than  above  ; fo  that  they  ferve  to  fup- 
ply  each  others  deficiencies  in  both  thofe  parts. 

On  the  external  fide  of  this  bone,  we  obferve 
a fmall  cavity  which  is  deftined  to  receive  the 
lower  end  of  the  ulna  ; and  its  lower  extremity 
is  formed  into  a large  cavity,  by  means  of  which 
it  is  articulated  with  the  bones  of  the  wrift,  and 
on  this  account  it  is  fometimes  called  manubrium 
ma?ms.  It  fupports  the  two  firft  bones  of  the 
wrift  on  the  fide  of  the  thumb,  whereas  the  ulna 
is  articulated  with  that  bone  of  the  wrift  which 
correfponds  with  the  little  finger. 

Through  the  whole  length  both  of  this  bone 
and  the  ulna,  a ridge  is  obferved-,  which  af- 
fords attachment  to  an  interolTeous  ligament. 
This  ligament  fills  up  the  fpace  between  the  two 
bones. 

3.  Bones  of  the  Hand, 

The  carpus  or  wrift  confifts  of  eight  fmall 

bones 

(i)Tke  motions  of  pronation  and  fiipination  maybe  eail- 
ly  defcribed.  If  the  palm  of  the  hand,  for  inftance,  is  placed 
on  the  furface  of  a table,  the  hand  may  be  faid  to  be  in  a ftate 
of  pronation  ; but  if  the  back  part  of  the  hand  is  turned  to- 
wards the  table,  the  hand  will  be  then  in  a ftate  of  fupination. 


I 21 


Pae^t  I.  OSTEOLOGY, 
bones  of  an  irregular  fhape,  and  difpofed  in 
two  unequal  rows.  Thole  of  the  upper  row 
are  articulated  with  the  bones  of  the  fore-arm, 
and  thofe  of  the  lower  one  vrith  the  metacarpus. 

The  ancient  anatomifts  delcilbed  thefe  bones 
numerically  ; Lyferus  feems  to  have  been  the 
firft  who  gave  to  each  of  them  a particular  name, 

Tiie  names  he  adopted  are  founded  on  the  fi- 
gure of  the  bones,  and  are  now  pretty  general- 
ly received,  except  the  firft,  which  inftead  of 
X OTVXOUef'i^  (the  name  given  to  it  by  Lyferus,  on 
account  of  its  finus  that  admits  a part  of  the  os 
magnum),  has  by  later  writers  been  named  Scap- 
hoides  or  Naviculare.  This,  which  is  the  outer- 
moft  of  the  upper  row  (confidering  the  thumb  as 
the  outer  fide  of  the  hand)  is  articulated  with 
the  radius  ; on  its  inner  fide  it  is  connected  v/ith 
the  os  lunare,  and  below  to  the  trapezium  and 
trapezoides.  Next  to  this  is  a fmaller  bone,  called 
the  os  lunare : becaufe  its  outer  fide,  which  is 
connected  with  the  fcaphoides,  is  fhaped  like  a 
crefcent.  This  is  likewife  articulated  with  the 
radius.  On  its  inner  fide  it  joins  the  os  cunei- 
forme,  and  anteriorly,  the  os  magnum  and  os 
unciforme. 

The  os  cuneiforme,  which  is  the  third  bone  in 
the  upper  row,  is  compared  to  a wedge,  from 
its  being  broader  above,  at  the  back  of  the 
hand,  than  it  is  below.  Pofteriorly  it  is  articu- 
lated with  the  ulna,  and  anteriorly  with  the  os 
uncjforme. 


Thefe 


122 


OSTEOLOGY.  Part  I. 

Thefe  three  bones  form  an  oblong  articulating 
furface,  covered  by  cartilage,  by  which  the  hand 
is  connedied  with  the  fore-arm. 

The  os  pififorme,  or  pea-like  bone,  which  is 
fmaller  than  the  three  jull  now  defcribed,  though 
generally  claffed  with  the  bones  of  the  upper  row, 
does  not  properly  belong  to  either  feries,  being 
placed  on  the  under  furface  of  the  os  cuneiforme, 
fo  as  to  projed;  into  the  palm  of  the  hand.  The 
four  bones  of  the  fecond  row  correfpond  with 
the  bones  of  the  thumb  and  fingers ; the  firft, 
fecond,  and  fourth,  are  from  their  lhapes  named 
trape'ztum^  trapezoidcs^  and  unciforme;  the  third, 
from  its  being  the  largeft  bone  of  the  carpus,  is 
fcyled  os  mag7ium. 

All  thefe  bones  are  convex  towards  the  back, 
and  flightly  concave  towards  the  palm  of  the 
hand ; their  articulating  furfaces  are  covered  with 
cartilages,  and  fecured  by  many  ftrong  ligaments, 
particularly  by  two  ligamentous  expanfions,  call- 
ed the  external  and  internal  annular  ligaments  of 
the  wrift.  The  former  extends  in  an  oblique 
diredtion  from  the  os  pififorme  to  the  ftyloid  pro- 
cefs  of  the  radius,  and  is  an  inch  and  an  half  in 
breadth  ; the  latter  or  internal  annular  ligament 
is  ftretched  from  the  os  pififorme  and  os  iinci- 
forme,  to  the  os  fcaphoides  and  trapezium.  Thefe 
annular  ligaments  likewife  ferve  to  bind  down 
the  tendons  of  the  wrifi  and  fingers. 

The  metacarpus  confifts  of  four  bones,  which 
fupport  the  fingers  ; externally  they  are  a little 

convex. 


PartI.  osteology.  123 

convex,  and  internally  fomewhat  concave,  where 
they  form  the  palm  of  the  hand.  They  are  hol- 
low, and  of  a cylindrical  fhape. 

At  each  extremity  they  are  a little  hollowed 
for  their  articulation  j fuperiorly  with  the  bones 
of  the  carpus,  and  inferiorly  with  the  firft  phalanx 
of  the  lingers,  in  the  fame  manner  as  the  feveral 
phalanges  of  the  fingers  are  articulated  with  each 
other. 

The  Jivs  Jingers  of  each  hand  are  compofed 
of  fifteen  bones,  difpofed  in  three  ranks  called 
phalanges : The  bones  of  the  firft  phalanx,  which 
are  articulated  with  the  metacarpus,  are  the  largeft, 
and  thofe  of  the  laft  phalanx  the  fmalleft.  Ail 
thefe  bones  are  larger  at  their  extremities  tha.n  iir 
their  middle  part. 

We  obferve  at  the  extremities  ©f  the  bones 
of  the  carpus,  metacarpus,  and  fingers,  feve- 
ral inequalities  that  ferve  for  their  articulation 
with  each  other ; and  thefe  articulations  arc 
ftrengthened  by  means  of  the  ligaments  \vhich 
furround  them. 

It  will  be  eafily  underftood  that  this  multipli- 
city of  bones  in  the  hand  (for  there  are  27  in  each 
hand)  is  eflential  to  the  different  motions  we  wilh 
to  pefform-  If  each  finger  was  compofed  only 
of  one  bone  inftead  of  three,  it  would  be  impoffi- 
blc  for  us  to  grafp  any  thing. 


§2.  Of 


124  OSTEOLOGY.  Part  I. 

^ 2.  Of  the  Lower  Extremities. 

Each  lower  extremity  is  divided  into  four 
parts,  viz.  the  os  femoris,  or  thigh  bone  ; the 
rotula,  or  knee-pan  ; the  leg  and  the  foot. 

I.  Of  the  Thigh. 

The  os  femoris.  The  thigh  is  compofed  only 
of  this  bone,  which  is  the  largeft  and  ftrongeft 
we  have.  It  will  be  neceffary  to  diftinguifh  its 
body  and  extremities : Its  body,  which  is  of  a 
cylindrical  fhape,  is  convex  before  and  con- 
cave behind,  where  it  ferves  to  lodge  feveral 
mufcles. 

Throughout  two-thirds  of  its  length  we  obferve 
a ridge  called  Itnea  afpera.,  which  originates  from 
the  trochanters,  and  after  running  for  fome  way 
downwards,  divides  into  two  branches,  that  ter- 
minate in  the  tuberofities  at  the  lower  extremity 
of  the  bone. 

At  its  upper  extremity  we  muft  defcribe  the 
neck  and  fmooth  head  of  the  bone,  and  likewife 
two  confiderable  procelTes : The  head,  which 
forms  the  greater  portion  of  a fphere  unequally 
divided,  is  turned  inwards,  and  received  into  the 
great  cotyloid  cavity  of  the  os  innominatum.  At 
this  part  of  the  bone  there  is  a little  foffa  to  be 
obferved,  to  which  the  round  ligament  is  attach- 
ed, and  which  we  have  already  defcribed  as  tend- 
ing to  fecure  the  head  of  this  bone  in  the  great 

acetabulum. 


Part  I.  OSTEOLOGY.  125 

acetabulum.  The  neck  is  almoft  horizontal,  con- 
fidered  with  refpeft  to  its  fituation  with  the  body 
of  the  bone.  Of  the  two  procefles,  the  external 
one,  which  is  the  largeft,  is  called  trochanter 
major  ; and  the  other,  which  is  placed  on  the 
infide  of  the  bone,  trochanter  minor.  They  both 
afford  attachment  to  mufcles.  The  articulation 
of  the  os  femoris  with  the  trunk  is  ftrengthened 
by  means  of  a capfular  ligament,  which  adheres 
every  ,where  round  the  edge  of  the  great  cotyloid 
cavity  of  the  os  innominatum,  and  furrounds  the 
head  of  the  bone. 

The  os  femoris  moves  upon  the  trunk  in  evei*y 
diredfion. 

At  the  lower  extremity  of  the  bone  are  two 
proteffes  called  the  condyles,  and  an  intermedi- 
ate fmooth  cavity,  by  means  of  which  it  is  arti- 
culated with  the  leg  by  ginglimus. 

All  round  the  under  end  of  the  bone  there  is 
an  irregular  furface  where  the  capfular  ligament 
of  the  joint  has  its  origin,  and  where  blood-veffels 
go  into  the  fubftance  of  the  bone. 

Between  the  condyles  there  is  a cavity  pofte- 
Aorly,  in  which  the  blood-veffels  and  nerves 
are  placed,  fecure  from  the  compreffion  to  which 
they  would  otherwife  be  expofed  in  the  adfion 
of  bending  the  leg,  and  which  would  not  fail  to 
be  hurtful. 

At  the  fide  of  each  condyle  externally,  there 
is  a tuberofity,  from  whence  the  lateral  ligaments 
originate,  which  are  extended  down  to  the  tibia. 

A 


126  OSTEOLOGY.  Part  I. 

A ligament  likewife  arifes  from  each  condyle 
pofteriorly.  One  of  thefe  ligaments  pafles  from 
the  right  to  the  left,  and  the  other  from  the 
left  to  the  right,  fo  that  they  interfe6t  each 
other,  and  for  that  reafon  are  called  the  crofs  li- 
gaments. 

The  lateral  ligaments  prevent  the  motion  of 
the  leg  upon  the  thigh  to  the  right  or  left ; and 
the  crofs  ligaments,  which  are  alfo  attached  to 
the  tibia,  prevent  the  latter  from  being  brought 
forwards. 

In  new-born  children  all  the  proceffes  of  this 
bone  are  cartilaginous. 

2.  The  Rotula,  or  Knee-pan. 

The  rotula,  patella,  or  knee-pan,  as  it  is  dif- 
ferently called,  is  a flat  bone  about  four  or  five 
inches  in  circumference,  and  is  placed  at  the  fore- 
part of  the  joint  of  the  knee.  In  its  Ihape  it  is 
fomewhat  like  the  common  figure  of  the  heart, 
with  its  point  downward. 

It  is  thinner  at  its  edge  than  in  its  middle  part ; 
at  its  fore-part  it  is  fmooth  and  fomewhat  con^ 
vex  ; its  pofterior  furface,  which  is  more  un- 
equal, affords  an  elevation  in  the  middle  which 
is  admitted  between  the  two  condyles  of  the  os 
femoris. 

This  bone  is  retained  in  its  proper  fituation  by 
a ftrong  ligament  which  every  where  furrounds 
it,  and  adheres  both  to  the  tibia  and  os  femoris  ; 


Part  I.  OSTEOLOGY.  127 

it  is  likewife  firmly  connected  with  the  tibia  by 
means  of  a ftrong  tendinous  ligament  of  an  inch 
in  breadth,  and  upwards  of  two  inches  in  length, 
which  adheres  to  the  lower  part  of  the  patella,  and 
to  the  tuberofity  at  the  upper  end  of  the  tibia. 
On  account  of  this  connection,  it  is  very  pro- 
perly confidered  as  an  appendage  to  the  tibia, 
which  it  follows  in  all  its  motions,  fo  as  to  be  to 
it  what  the  olecranon  is  to  the  ulna.  There  is 
this  difference,  however,  that  the  olecranon  is 
a fixed  procefs  ; whereas  the  patella  is  moveable, 
being  capable  of  Aiding  from  above  downv^^a^ds 
and  from  below  upwards.  This  mobility  is  ef- 
fential  to  the  rotatory  motion  of  the  leg. 

In  very  young  children  this  bone  is  entirely 
cartilaginous. 

The  principal  ufe  of  the  patella  feems  to  be 
to  defend  the  articulation  of  the  the  knee  from 
external  injury  ; it  likewife  tends  to  increafe  the 
power  of  the  extenfor  mufcles  to  the  leg,  by  re- 
moving their  direction  farther  from  the  centre 
of  motion  in  the  manner  of  a pulley. 

3.  Of  the  leg. 

The  leg  is  compofed  of  two  bones  ; Of  thefe 
the  inner  one,  which  is  the  largeft,  is  called  ti- 
bia ; the  other  is  much  fmaller,  and  named  fi- 
bula. 

The  TIBIA,  which  is  fo  called  from,  its  refem- 
blance  to  the  mufical  pipe  of  the  ancients,  has 

three 


128  OSTEOLOGY.  Part  I. 

three  furfaces,  and  is  not  veiy  unlike  a triangu- 
lar pril'm.  Its  pofterior  furface  is  the  broadeft  ; 
anteriorly  it  has  a confiderable  ridge  called  the 
Ihin,  between  which  and  the  ildn  there  are  no 
mufcles.  At  the  upper  extremity  of  this  bone 
are  two  furfaces,  a little  concave,  and  feparated 
from  each  other  by  an  intermediate  elevation. 
The  two  little  cavities  receive  the  condyles  of 
the  os  femoris,  and  the  eminence  between 
them  is  admitted  into  the  cavity  which  we  fpoke 
of  as  being  between  the  two  condyles ; fo  that 
this  articulation  affords  a fpecimen  of  the  com- 
plete ginglimus.  Under  the  external  edge  of 
the  upper  end  of  this  bone  is  a circular  flat  fur- 
face,  which  receives  the  head  of  the  fibula. 

At  the  lower  and  inner  portion  of  the  tibia, 
we  obferve  a confiderable  procefs  called  mal- 
leolus internus.  The  bafis  of  the  bone  termi- 
nates in  a large  tranverfe  cavity,  by  which  it  is 
articulated  with  the  uppermoft  bone  of  the 
foot.  It  has  likewife  another  cavity  at  its  lower 
end  and  outer  fide,  which  is  fomewhat  oblong, 
and  receives  the  lower  end  of  the  fibula. 

The  tibia  is  hollow  through  its  whole  length. 

The  FIBULA  is  a final  1 long  bone  fituated  on 
the  outfide  of  the  tibia.  Its  fuperior  extremity 
does  not  reach  quite  fo  high  as  the  upper  part  of 
the  tibia,  but  its  lower  end  defcends  fomewhat 
lower.  Both  above  and  below,  it  is  articulated 
wdth  the  tibia  by  means  of  the  lateral  cavities  we 
poticed  in  our  defcription  of  that  bone. 

3 


Its 


Part  I.  OSTEOLOGY.  129 

Its  lower  extremity  is  ftretched  out  into  a co- 
ronoid  procefs,  which  is  flattened  at  its  infide, 
and  is  convex  externally,  forming  what  is  called 
the  malleolus  extemus^  or  outer  ancle.  This  is 
rather  lower  than  the  malleolus  internus  of  the 
tibia. 

The  body  of  this  bone,  which  is  in'egularly 
triangular,  is  a little  hollow  at  its  internal  fur- 
face,  which  is  turned  towards  the  tibia  ; and  it 
affords  like  that  bone,  through  its  whole  length, 
attachment  to  a ligament,  which  from  its  litua- 
tion  is  called  the  interoffeous  ligament. 

4.  Of  the  foot. 

The  foot  confifls  of  the  tarfus,  metatarfus,  and 
toes. 

The  TARSUS  is  compofed  of  feven  bones, 
viz.  the  aftragalus,  os  calcis,  os  naviculare, 
os  cuboid^s,  and  three  others  called  cuneiform 
bones. 

The  ASTRAGALUS  isa  large  bone  with  which 
both  the  tibia  and  fibula  are  articulated.  It  is 
the  uppermofl  bone  of  the  foot ; it  has  feveral 
furfaces  to  be  confidered ; its  upper,  and  fome- 
what  poflerior  part,  which  is  fmooth  and  con- 
vex, is  admitted  into  the  cavity  of  the  tibia.  Its 
lateral  parts  are  connected  with  the  malleoli  of 
the  two  bones  of  the  leg  ; below,  it  is  articula- 
ted with  the  os  calcis,  and  its  anterior  furface  is 

I received 


130  OSTEOLOGY. 

received  by  the  os  naviculare.  All  thefe  arti- 
culations are  fecured  by  means  of  ligaments. 

The  os  CALCis,  or  calcaneiim,  which  is  of 
a very  irregular  figure,  it  is  the  iargeft  bone  of 
the  foot.  Behind,  it  is  formed  into  a confider- 
able  tuberofity  called  the  heel ; without  this  tu- 
berofity,  which  fupports  us  in  an  eredf  pofture, 
and  when  we  walk,  we  fhould  be  liable  to  fall 
backwards. 

On  the  internal  furface  of  this  bone,  we  ob- 
ferve  a confiderable  fmuofity,  which  affords  a 
paffage  to  the  tendon  of  a mufcle  ; and  to  the  pof- 
terior  part  of  the  os  calcis,  a ftrong  tendinous 
cord  called  tendo  achillis  (m)  is  attached,  which 
is  formed  by  the  tendons  of  feveral  mufcles  uni- 
ted together.  The  articulation  of  this  with  the 
other  bones  is  fecured  by  means  of  ligaments. 

The  Os  NAVICULARE,  or  fcaphoides,  (for 
thefe  two  terms  have  the  fame  fignification),  is 
fo  called  on  account  of  its  refemblance  to  a little 
hark.  At  its  pofterior  part,  which  is  concave, 
it  receives  the  aftragalus ; anteriorly  it  is  articu- 
lated with  the  cuneiform  bones,  and  laterally  it 
is  connected  with  the  os  cuboides. 

The  os  CUBOIDES  forms  an  irregular  cube. 
Pofteriorly  ft  is  articulated  with  the  os  calcis  j 
anteriorly  it  fupports  the  two  laft  bones  of  the 
metatarfus,  and  laterally  it  joins  the  third  cunei- 
form bone  and  the  os  naviculare. 

Each 

(m)  This  tendon  isfometimes  ruptured  bj^jumping,  danc- 
ing, or  other  violent  efforts. 


Part  I.  OSTEOLOGY.  131 

Each  of  the  OSSA  cuneiformia,  whichare 
three  in  number,  refembles  a wedge,  and  from 
this  fimilitude  their  name  is  derived.  They  are 
placed  next  to  the  metatarfus  by  the  lides  of  each 
other,:  and  are  ufually  diftinguilhed  into  os  cu- 
neiforme  externum^  medium  or  minimum^  and  in- 
ternum or  maximum.  The  fuperior  furface  of 
thefe  bones,  from  their  wedge-like  Ihape,  is 
broader  than  that  which  is  below,  where  they 
help  to  form  the  foie  of  the  foot ; pofteriorly 
they  are  united  to  the  os  naviculare,  and  ante- 
riorly they  fupport  the  three  firft  metatarfal 
bones. 

When  thefe  feven  bones  compofmg  the  tarfus 
are  viewed  together  in  the  fkeleton,  they  appeat 
convex  above,  where  they  help  to  form  the  up- 
per part  of  the  foot ; and  concave  underneath, 
where  they  form  the  hollow  of  the  foot,  in 
which  the  veffels,  tendons  and  nerves  of  the 
foot  are  placed  fecure  from  prelTure. 

They  are  united  to  each  other  by  very  ftrong 
ligaments,  and  their  articulation  with  the  foot  is 
fecured  by  a cafpular  and  two  lateral  ligaments  j 
each  of  the  latter  is  covered  by  an  annular  liga- 
ment of  confiderable  breadth  and  thicknefs,  which 
ferves  to  bind  down  the  tendons  of  the  foot, 
and  at  the  fame  time  to  ftrengthen  the  articula- 
tion. 

The  oscuneiforme  externum  is  joined  laterally 
to  the  os  cuboides. 

Thefe  bones  complete  our  account  of  the  tar- 
I 2 fus. 


132  OStEOLOGY.  Part  I. 

fus.  Though  what  we  have  faid  of  this  part  of 
the  ofteology  has  been  very  fimple  and  concife, 
yet  many  readers  may  not  clearly  underhand  it : 
but  if  they  will  be  pleafed  to  view  thefe  bones 
in  their  proper  fituation  in  the  fkeleton,  all  that 
we  have  faid  of  them  will  ■ ■ eafily  underftood. 

The  METATARSUS  is  made  up  of  five  bones, 
whereas  the  metacarpus  confifts  only  of  four. 
The  caufe  of  this  difference  is,  that  in  the  hand 
the  laft  bone  of  the  thumb  is  not  included  among 
the  metacarpal  bones ; whereas  in  the  foot  the 
great  toe  has  only  two  bones.  The  firft  of  thefe 
bones  fupports  the  great  toe  and  is  much  larger 
than  the  reft,  which  nearly  refemble  each  other 
in  fize. 

Thefe  bones  are  articulated  by  one  extremity 
with  the  cuneiform  bones  and  the  os  cuboides, 
and  by  their  other  end  with  the  toes. 

Each  of  the  toes,  like  the  fingers,  confifts 
of  three  bones,  except  the  great  toe,  which  is 
formed  of  two  bones.  Thofe  of  the  other  four  are 
diftinguifhed  into  three  phalanges.  Although  the 
toes  are  more  confined  in  their  motion  than  the  fin- 
gers, yet  they  appear  to  be  perfedUy  fitted  for  the 
purpofes  they  are  defignedfor.  In  walking,  the  toes 
bring  the  centre  of  gravity  perpendicular  to  the 
advanced  foot ; and  as  the  foies  of  the  foot  are 
naturally  concave,  we  can  at  pleafure  increafe 
this  cavity,  and  form  a kind  of  vault,  which  ad- 
jufts  itfelf  to  the  different  inequalities  that  occur 
to  us  in  walking  ; and  which,  without  this  mode 

of 


Part  I.  OSTEOLOGY.  133 

of  arrangement,  would  incommode  us  exceed- 
ingly, efpecially  when  bare-footed. 

§ 4.  the  OJfa  Sesamoidea. 

Besides  the  bones  we  Lave  already  defcrib- 
ed,  there  are  feveral  fmall  ones  that  are  met  with 
only  in  the  adult  fkeleton,  and  in  perfons  who 
are  advanced  in  life  ; which,  from  their  fuppof- 
cd  general  refemblance  to  the  feeds  of  the  fela- 
mum,  are  called  oJJ'a  fefamoidea.  They  are  com- 
monly to  be  feen  at  the  firft  joint  of  the  great 
toe,  and  fometimes  at  the  joints  of  the  thumb  ^ 
they  are  likewife  now  and  then  to  be  found  at  the 
lower  extremity  of  the  fibula,  upon  the  con- 
fiyles  of  the  thigh-bone,  under  the  os  cuboides 
of  the  tarfus,  and  in  other  parts  of  the  body. 
Their  fize  and  number  feem  conftantly  to  be  in- 
creafed  by  age  and  hard  labour  ; and  as  they  are 
generally  found  in  fituations  where  tendons  and 
ligaments  are  moft  expofed  to  the  adtion  of 
mufcles,  they  are  now  generally  confidered  as 
ofiified  portions  of  ligaments  or  tendons. 

The  upper  furface  of  thefe  bones  is  ufually 
convex,  and  adherent  to  the  tendon  that  covers 
it ; the  fide  which  is  next  to  the  joint  is  fmooth 
and  flat.  Though  their  formation  is  accidental, 
yet  they  feem  to  be  of  fome  ufe,  by  raifmg  tjbe 
tendons  farther  from  the  centre  of  motion,  and 
confequently  increafing  the  power  of  the  muf- 
cles. In  the  great  toe  and  thumb  they  are  like- 
wife 


134  OSTEOLOGY.  Part  I. 

wife  ufeful,  by  forming  a groove  for  the  flexor 
tendons. 

EXPLANATION  of  the  Pl.ATES  of  OSTEOLOGY. 

Plate  XIX. 

Fig.  I.  A front  view  of  the  Male  Skeleton. 

A,  The  os  frontis.  B,  The  os  parietale.  C, 
The  coronal  future.  D,  The  fquamous  part  of 
the  temporal  bones.  E,  The  fquamous  future. 
F,  The  zygoma.  G,  The  maftoid  procefs.  H, 
The  temporal  procefs  of  the  fpenoid  bone.  I, 
The  orbit.  K,  The  os  maldS.  L,  The  os  max- 
illare  fuperius.  M,  Its  nafal  procefs.  N,  The 
ciTa  nafi.  O,  The  os  unguis.  P,  The  maxilla  in- 
ferior. Q^,  The  teeth,  which  are  fixteen  in 
number  in  each  jaw.  R,  The  feven  cervical  ver- 
tebrae, with  their  intermediate  cartilages.  S, 
Their  tranfverfe  proceffes.  T,  The  twelve  dor- 
fal  vertebrae,  with  their  intermediate  cartilages. 
U,  The  five  lumbar  vertebrae.  V,  Their  tranf- 
verfe proceffes.  W,  The  upper  part  of  the  os 
facrum,  X,  Its  lateral  parts.  The  holes  feen 
on  its  fore  part  are  the  paffages  of  the  under- 
moft  fpinai  nerves  and  fmall  veffels.  Oppofite 
to  the  holes,  the  marks  of  the  original  divifions 
of  the  bone  are  feen.  Y,  The  os  ilium.  Z,  Its 
creft  or  fpine.  a.  The  anterior  fpinous  pro- 

cefles. 


Part  L OSTEOLOGY.  135 

cefles.  b,  The  brim  of  the  pelvis,  c,  The  if- 
chiatic  niche,  d,  The  os  ifchium.  e,  Its  tube- 
rofity.  f,  Its  fpinous  procefs.  g,  Its  cms.  h. 
The  foramen  thyroldeum.  i,  The  os  pubis,  k, 
The  fymphyfis  pubis.  1,  The  crus  pubis,  m, 
The  acetabulum,  n,  The  feventh  or  lafl  true 
rib.  o,  The  twelfth  or  lafl:  falfe  rib.  p,  The  up- 
per end  of  the  fternum.  q,  The  middle  piece, 
r.  The  under  end,  or  cartilage  enfiformis.  s,  The 
clavicle,  t,  The  internal  furface  of  the  fcapula. 
u,  Its  acromion,  v,  Its  coracoid  procefs.  vr,  Its 
cervix,  x,  The  glenoid  cavity,  y,  The  os  hu- 
meri. z,  Its  head,  which  is  coniiedfed  to  the 
glenoid  cavity,  i,  Its  external  tubercle.  2,  Its 
internal  tubercle.  3,  The  groove  for  lodging 
the  long  head  of  the  biceps  mufcle  of  the  arm. 
4,  The  internal  condyle.  5,  The  external  con- 
dyle. Between  4 and  5,  the  trochlea.  6.  The 
radius,  y,  Its  head.  8,  Its  tubercle.  9,  The  ulna. 
JO,  Its  coronoid  procefs.  11,12,  13,  14,  15, 
16,  17,  18,  The  carpus  ; compofed  of  os  na- 
viculare,  os  lunare,  os  cuneiforme,  os  pihforme, 
os  trapezium,  os  trapezoides,  os  magnum,  os 
unciforme.  1 9,  The  five  bones  of  the  metacar- 
pus, 20,  The  two  bones  of  the  thumb.  21, 
The  three  bones  of  each  of  the  fingers.  22,  The 
os  femoris.  23,  Its  head.  24,  Its  cei^^ix.  25, 
The  trochanter  major.  26,  The  trochanter  mi- 
nor. 27,  The  internal  condyle.  28,  The  ex- 
ternal condyle.  29,  The  rotula.  30,  The  tibia, 
3 1,  Its  head.  32,  Its  tubercle,  33,  Its  fpine. 

34.  The 


136  OSTEOLOGY,  Part  I. 

34,  The  malleolus  internus.  35,  The  fibula. 

36,  Its  head.  37.  The  malleolus  externus.  The 
tarfus  is  compofed  of,  38,  The  aftragalus  ; 39, 

The  os  calcis;  40,  The  os  naviculare ; 41,  Three 
ofla  cuneiformia,  and  the  os  cuboides,  which  is 
notfeen  in  this  figure.  42,  The  five  bones  of 
the  metatarfus.  43,  The  two  bones  of  the  great 
toe.  44,  The  three  bones  of  each  of  the  fmall 
toes. 

Fig.  2.  A front  view  of  the  Skull. 

A,  The  os  frontis.  B,  The  lateral  part  of  the 
os  frontis,  which  gives  origin  to  part  of  the  tem- 
poral mufcle.  C,  The  fuperciliary  ridge.  D, 

The  fuperciliary  hole  through  which  the  frontal 
veflels  and  nerves  pafs.  EE,  The  orbitar  pro- 
cefies.  F,  The  middle  of  the  tranfverfe  future. 

G,  The  upper  part  of  the  orbit.  H,  The  fora- 
me¥i  opticum.  I,  The  foramen  lacerum.  K, 

The  infei'ior  orbitar  filTure.  L,  The  os  unguis 
M,  The  offa  nafi.  N,  The  os  maxillare  fuperius. 

O,  Its,  nafal  procefs,  P,  The  external  orbitar 
hole  through  which  the  fuperior  maxillary  vef- 
fels  and  nerves  pafs,  Q^,  The  03  malae.  R,  A 
paffage  for  fmall  veflels  into,  or  out  of  the  orbit. 

S,  The  under  part  of  the  left  noftril.  T,  The 
feptum  narium.  U.  The  os  fpongiofum  fupe- 
rius.  V,  The  os  fpongiofum  infernus.  W,  The 
edge  of  the  alveoli,  or  fpongy  fockets,  for  the  1 

teeth. 


Part  I.  OSTEOLOGY.  137 

teeth.  X,  The  maxilla  inferior.  Y,  The  paf- 
fage  for  the  inferior  maxillary  veflels  and  nerves. 

Fig.  3.  A fide-view  of  the  Skull. 

A,  The  os  frontis.  B,  The  coronal  future. 
C,  The  os  parietale.  D,  An  arched  ridge  which 
gives  origin  to  the  temporal  mufcle.  E,  The 
fquamous  future.  F,  The  fquamous  part  of  the 
temporal  bone  ; and,  farther  forwards,  the  tem- 
poral procefs  of  the  fphenoid  bone.  G,  The  zy- 
gomatic procefs  of  the  temporal  bone.  H,  The 
zygomatic  future.  I,  The  maftoid  procefs  of  the 
temporal  bone.  K,  The  meatus  auditorius  ex- 
ternus.  L,  The  orbitar  plate  of  the  frontal  bone, 
under  which  is  feen  the  tranfverfe  future.  M, 
The  pars  plana  of  the  ethmoid  bone.  N,  The 
os  unguis.  O,  The  right  os  nafi.  P,  The  fu- 
perior  maxillary  bone.  Q^,  Its  nafal  procefs. 
R,  The  two  dentes  incifores.  S,  The  dens  ca- 
ninus.  T,  The  two  molaies.  U,  The  three 
large  molares.  V,  The  os  malae.  W,  The 
lower  jaw.  X,  Its  angle.  Y,  The  coronoid 
procefs.  Z,  The  condyloid  procefs,  by  which 
the  jaw  is  articulated  with  the  temporal  bone. 

Fjg.  4.  The  pofterior  and  right  fide  of  the 
Skull. 

A,  The  os  frontis.  BB,  The  olfa  parietalia. 
C,  The  fagittal  future.  D,  The  parietal  hole, 
through  which  a fmall  vein  runs  to  the  fuperior 

longitu-r 


138  OSTEOLOGY.  Part  L 

longitudinal  linus.  E.  The  lambdoid  future. 
FF,  OfTa  triquetra.  G,  The  os  occipitis.  H, 
The  fquamous  part  of  the  temporal  bone.  I, 
The  maftoid  procefs.  K,  The  zygoma.  L,  The 
os  malsE.  M,  The  temporal  part  of  the  fphenoid 
bone.  N,  The  fuperior  maxillary  bone  and 
teeth. 

Fig.  5.  The  external  Surface  of  theOspRONTis, 

A,  The  convex  part.  B,  Part  of  the  tempo- 
ral folTa.  C,  The  external  angular  procefs.  I)^ 
The  internal  angular  procefs.  E,  The  nafal 
procefs.  F,  The  fuperciliary  hole.  H,  The 
orbitar  pla,te. 

Fig.  6.  The  interior  furface  of  the  Os  FronTiS. 

AA,  The  ferrated  edge  which  affifts  to  form 
the  coronal  future.  B,  The  external  angular 
procefs.  C,  The  internal  angular  procefs.  D, 
The  nafal  procefs.  E,  The  orbitar  plate.  F,  The 
cells  which  correfpond  with  thofe  of  the  eth- 
moid bone.  G,  The  paffage  from  the  frontal 
fmus.  H,  The  opening  which  receives  the  cri- 
briform plate  of  the  ethmoid  bone.  I,  The  ca- 
vity which  lodges  the  fore  part  of  the  brain.  K, 
The  fpine  to  which  the  falx  is  fixed.  L,  The 
groove  which  lodges  the  fuperior  longitudinal 
fmus. 


PlatR 


Part  L 


OST’EOLOGY. 


139 

Plate  aX. 

Fig.  I.  A back  view  of  the  Skeleton. 

AA,  The  offa  parietalia.  B,  The  fagittal  fu- 
ture. C,  The  lambdoid  future.  D,  The  occi- 
pital bone.  E,The  fquamous  future.  F,  The  maf- 
toid  procefs  of  the  temporal  bone.  G,  The  os 
malse.  H,  The  palate  plate  of  the  fuperior  max- 
illary bones.  I,  T he  maxilla  inferior.  K,  The 
teeth  of  both  jaws.  L,  The  feven  cervical  ver- 
tebrsE.  M,  Their  fpiiious  proceffes.  N,  Their 
tranfverfe  and  oblique  proceffes.  O,  The  laft  of 
•the  twelve  dorfal  vertebra.  P,  The  fifth  or 
laft  lumbar  vertebra.  The  tranfverfe  pfo- 

celTes.  R,  The  oblique  procefl'es.  S,  The  fpi- 
nous  procefles.  T,  The  upper  part  of  the  os 
facrum.  U,  The  pofterior  holes  which  tranf- 
mit  fmall  blood-veflels  and  nerves.  V,  The  un- 
der part  of  the  os  facrum  which  is  covered  by  a 
membrane.  W,  The  os  coccygis.  , X,  The  os 
ilium.  Y,  Its  fpine  or  creft.  Z,  The  ifchi- 
atic  niche,  a,  The  os  ifchium.  b,  Its  tubero- 
fity.  c,  Its  fpine.  d,  The  os  pubis,  e,  The  forar 
men  hydroideum.  f,  The  feventh  or  laft  true  rib, 
g,  The  twelfth  or  laft  falfe  rib.  h,  The  clavicle, 
i,  The  fcapula.  k,  its  fpine.  1,  Its  acromion, 
m,  Its  cervix,  n,  Its  fuperior  cofta.  o,  Its  pofterior 
cofta.  p,  Its  inferior  cofta.  q,  The  os  humeri, 
r,  The  radius,  s,  The  ulna,  t,  Its  olecranon,  u, 
All  the  bones  of  the  carpus,  exceting  the  os 

pififorme, 


140  OSTEOLOGY.  Part  I. 

plfiforme,  which  is  feen  in  Plate  XIX.  fig.  i. 
V,  The  five  bones  of  the  metacarpus,  w,  The 
two  bones  of  the  thumb,  x,  The  three  bones 
of  each  of  the  fingers,  y,  The  two  fefamoid 
bones  at  the  root  of  the  left  thumb,  z,  The  os 
femoris.  i , The  trochanter  major.  2,  The  tro- 
chanter minor.  3,  The  linea  afpera.  4,  The 
internal  condyle.  5,  The  external  condyle.  6 6, 
The  femilunar  cartilages.  7,  The  tibia.  8,  The 
malleolus  internus.  9,  The  fibula.  10,  The 

malleolus  externus.  11,  The  tarfus.  12,  The 
metatarfus.  13,  The  toes. 

Fig.  2.  The  external  Surface  of  the  left  Os  Pa- 

RIETALE. 

A,  The  convex  fmooth  furface.  B,  The  pa- 
rietal hole.  C,  An  arch  made  by  the  beginning 
of  the  temporal  mufcle. 

Fig  3.  The  intern^  Surface  of  the  fame  bone. 

A,  Itsfuperior  edge,  which,  joined,  with  the 
other,  forms  the  fagittal  future.  B,  The  anterior 
edge,  which  alfifts  in  the  formation  of  the  co- 
ronal future.  C.  The  inferior  edge  for  the  fqua- 
mous  future.  D,  The  pofterior  edge  for  the 
lambdoid  future.  E,  A depreffion  made  by  the 
latera,!  finus.  FF,  The  prints  of  the  arteries  of 
the  dura  mater. 

Fig.  4. 


Part  I.  OSTEOLOGY.  141 

Fig.  4.  The  external  Surface  of  the  Left  OsTem- 

PORUM. 

A,  The  fquamous  part.  B,  The  maftoid  pro- 
cefs.  C,  The  zygomatic  procefs.  D,  The  fty- 
loid  procefs.  E,  The  petrofal  procefs.  F,  The 
meatus  auditorius  externus.  G,  The  glenoid 
cavity  for  the  articulation  of  the  lower  jaw.  H, 
The  foramen  ftylo-maftoideum  for  the  portio 
dura  of  the  feventh  pair  of  nerves.  I,  Paflages 
for  blood-veflels  into  the  bone.  K,  The  fora- 
men maftoideum  through  which  a vein  goes  to 
the  lateral  finus. 

Fig.  5.  The  Internal  furface  of  the  Left  Os  T em- 

PORUM. 

A,  The  fquamous  part ; the  upper  edge  of 
which  affifts  in  forming  the  fquamous  future.  B, 
The  maftoid  procefs.  C,  The  ftyloid  procefs.  D, 
The  pars  petrofa.  E,  The  entry  of  the  feventh 
pair,  or  auditory  nerve.  F,  The  foffa,  which 
lodges  a part  of  the  lateral  finus.  G,  The  for- 
amen maftoideum. 

Fig.  6.  The  External  Surface  of  the  Osseous 

Circle,  which  terminates  the  meatus  audi- 

trius  externus. 

A,  The  anterior  part.  B,  A fmall  part  of  the 
groove  in  which  the  membrana  tympani  is  fixed. 

N.  B.  This,  with  the  fubfequent  bones  of  the 
ear,  are  here  delineated  as  large  as  the  life. 

Fig.  7. 


142 


OSTEOLOGY. 


Part  I. 


Fig,  7.  The  Internal  Surface  of  the  Osseous 
Circle. 

A,  The  anterior  part.  B,  The  groove  in 
which  the  membrana  tympani  is  fixed. 

Fig.  8.  The  fituation  and  connection  of  the 
fmall  Bones  of  the  Ear. 

A,  The  malleus.  B,  The  incus.  C,  The 
os  orbiculare.  D,  The  ftapes. 

Fig.  9.  The  Malleus,  with  its  Head,  Han- 
dle, and  Small  Procefles. 

Fig.  10.  The  Incus,  with  its  Body,  Superior 
and  Inferior  branches. 

Fig,  II.  The  Os  Orbiculare. 

Fig.  12.  The  Stapes,  with  its  Head,  Bafe,  and 
two  cura. 

Fig.  13.  An  Internal  View  of  theLBYARiNTii 
of  the  Ear. 

A,  The  hollow  part  of  the  cochlea,  which 
forms  a fhare  of  the  meatus  auditorius  intemus. 
B,  The  veftibulum.  CCC,  The  femicircular 
canals. 

Fig.  14.  An  External  View  of  the  Labyrinth. 

A,  The  femicircular  canals.  B,  The  feneftra 

ovalis- 


Part  I.  OSTEOLOGY.  143 

ovalis  which  leads  into  the  veftibulum.  C,  The 
feneftra  rotunda  which  opens  into  the  cochlea- 
D,  The  different  turns  of  the  cochlea. 

Fig  15.  The  Internal  Surface  of  the  Os  Sphe- 

NOIDES. 

A A,  The  temporal  proceffes.  B B,  The  pte- 
rygoid proceffes.  CC,  The  fpinous  proceffes; 
DD,  The  anterior  clinoid  proceffes.  E.  The 
pofterior  clinoid  procefs.  F,  The  anterior  pro- 
cefs  which  joins  the  ethmoid  bone.  G,  The 
fella  turcica  for  lodging  the  glandula  pituitaria. 
H,  The  foramen  opticum.  K,  The  foramen 
lacerum,  L,  The  foramen  rotundum.  M,  The 
foramen  ovale.  N,  The  foramen  fpinale. 

Fig.  16.  The  External  Surface  of  the  Os  Sphe- 

NOIDES. 

AA,  The  temporal  proceffes.  BB,  The 
pterygoid  proceffes.  CC,  The  fpinous  pro- 
ceffes. D,  The  proceffus  azygos.  E,  The  fmall 
triangular  proceffes  which  grow  from  the  body 
of  the  bone.  FF,  The  orifices  of  the  fpfienoid 
fmufes.  G,  The  foramen  lacerum.  H,  The 
foramen  rotundum.  I,  The  foramen  ovale.  K, 
The  foramen  pterygoideum. 

Fig.  17.  The  External  Tiew  of  the  Os  Eth- 

MOIDES. 

A,  The  nafal  lamella.  B B,  The  grooves  be- 
tween 


144  OSTEOLOGY.  Part!. 

tween  the  nafal  lamella  and  ofFa  fponglofa  fupe- 
riora.  CC,  The  oiTa  fponglofa  fuperiora.  DD, 
The  fphenoidal  cornua.  See  Fig.  1 6.  E. 

Fig.  1 8.  The  Internal  View  of  the  Os  Eth- 

MOIDES. 

A,  The  crilfa  galli.  B,  The  cribriform  plate, 
with  the  different  paffages  of  the  olfadory  nerves. 
CC,  Some  of  the  ethmoidal  cells.  D,  The  right 
os  planum.  EE,  The  fphenoidal  cornua. 

Fig.  19.  The  right  Sphenoidal  Cornu. 

Fig.  20.  The  left  Sphenoidal  Cornu. 


Fig.  21.  The  external  Surface  of  the  Os  Occi- 

PITIS. 

A,  The  upper  part  of  the  bone.  B,  The  fu- 
perior  arched  ridge.  C,  The  inferior  arched 
ridge.  Under  the  arches  are  prints  made  by  the 
mufclfis  of  the  neck.  DD,  The  two  condy- 
loid proceffes  which  articulate  the  head  with  the: 
fpine.  E,  The  cuneiform  procefs.  F,  The 
foramen  magnum  through  which  the  fpinal  mar- 
row paffes.  G G,  The  pofterior  condyloid  for- 
amina which  tranfmit  veins  into  the  lateral  fi- 
nufes.  HH,  The  foramina  lingualia  for  the 
paffage  of  the  nine  pair  of  nerves. 


1| 


3 


Fig.  22. 


PI;ttelX 


Part  I. 


OSTEOLOGY. 


H5 

Fig.  22.  The  Internal  Surface  of  the  Os  Occi- 

PITIS. 

A A,  The  two  fides  which  affift  to  form  the 
lambdoid  future.  B,  The  point  of  the  cunei- 
form procefs,  where  it  joins  the  fphenoid  bone. 
CC,  The  prints  made  by  the  pofterior  lobes  of 
the  brain.  DD,  Prints  made  by  the  lobes  of  the 
cerebellum.  E,  The  cruciform  ridge  for  the 
attachment  of  the  proceffes  of  the  dura  mater. 
F,  The  courfe  of  the  fuperior  longitudinal  fi- 
nufes.  GG,  The  courfe  of  the  two  lateral  fi- 
nufes.  H,  The  foramen  magnum.  1 1,  The 
pofterior  condyloid  foramina. 

Plate  XXL 

Fig.  I.  A Side-view  of  the  Skeleton. 

AA,  The  ofla  parietalia.  B,  The  fagittal  fu- 
ture. C,  The  os  occipitis,  DD,  The  lambdoid 
future.  E,  The  fquamous  part  of  the  temporal 
bone.  F,  The  maftoid  procefs.  G,  The  mea- 
tus auditorius  externus.  H,  The  os  frontis. 
I,  The  os  malse.  K,  The  os  maxillare  fupe- 
rius.  L,  The  maxilla  inferior.  M,  The  teeth 
of  both  jaws.  N,  The  feventh,  or  laft  cervical 
vertebra.  O,  The  fpinous  procefles.  P,  Their 
Tranfverfe  and  oblique  procefles.  Q^,  The 
twelfth  or  laft  dorfal  vertebra.  R,  The  fifth  or 
laft  lumbar  vertebra.  S,  The  fpinous  proceffes. 

K T,  Open- 


146  OSTEOLOGY.  Part  I. 

T,  Openings  between  the  vertebras  for  the  paf- 
fage  of  the  fpinal  nerves.  U,  The  under  end 
of  the  os  facrum.  V,  The  os  coccygis.  W,  The 
os  ilium.  X,  The  anterior  fpinous  proceffes. 
Y,  The  pofterior  fpinous  proceffes.  Z,  The 
ifchiatic  niche,  a,  The  right  os  ilium,  b,  The 
ofl'a  pubis,  c,  The  tuberofity  of  the  left  os  if- 
chium.  d,  The  fcapula.  e,  Its  fpine.  f,  The 
os  humeri,  g,  The  radius,  h,  The  ulna,  i, 
The  carpus,  k.  The  metacarpal  bone  of  the 
thumb.  1,  The  metacarpal  boneof  the  fingers, 
m,  The  two  bones  of  the  thumb,  n,  The  three 
bones  of  each  of  the  fingers,  o,  The  os  femoris. 
p,  Its  head,  q,  The  trochanter  major,  r,  The 
external  condyle,  s,  The  rotula.  t,  The  tibia, 
u,  The  fibula,  v,  The  malleolus  externus.  w, 
The  aftragalus.  x,  The  os  calcis.  y,  The  os 
naviculare,  z,  The  three  offa  cuneiformia.  i, 
The  os  cuboides.  2,  The  five  metatarfal  bones. 
3,  The  two  bones  of  the  great  toe.  4,  The 
three  bones  of  each  of  the  fmall  toes. 

Fig.  2.  A View  of  the  Internal  Surface  of  the 
Bafe  of  the  Skull. 

AAA,  The  two  tables  of  the  fkull  with  the 
diplbe.  BB,  The  orbitar  plates  of  the  frontal 
bone.  C,  The  crifta  galli,  with  cribriform  plate 
of  the  ethmoidal  bone  on  each  fide  of  it,  through 
which  the  firft  pair  of  nerves  pafs.  D,  The 
cuneiform  procefs  of  the  occipital  bone.  E. 
The  cruciform  ridge.  F,  The  foramen  mag- 
num 


! . Part  I.  OSTEOLOGY.  147 

< num  for  the  paiTage  of  the  fpinal  marrow.  G, 

; The  zygoma,  made  by  the  joining  of  the  zygo- 
I made  proceifes  of  the  os  temporum.  I,  The 
[ pars  mamillaris.  K,  The  pars  petrofa.  L,  The 
I temporal  procefs  of  the  fphenoid  bone.  MM, 
The  anterior  clinoid  procefles.  N,  The  pofte- 
rior  clinoid  procefs.  O,  The  fella  turcica.  P, 
The  foramen  opticum,  for  the  palTage  of  the  op- 
tic nerve  and  occular  artery  of  the  left  fide.  Q^, 
The  foramen  lacerum,  for  the  third,  fourth, 
fixth,  and  firft  of  the  fifth  pair  of  the  nerves 
and  ocular  vein.  R,  The  foramen  rotundum, 
for  the  fecond  of  the  fifth  pair.  T,  The  fora- 
men fpinale,  for  the  principal  artery  of  the  du- 
ra mater.  U,  The  entry  of  the  auditory  nerve. 
V,  The  paffage  for  the  lateral  finus.  W,  The 
paffage  of  the  eighth  pair  of  nerves.  X,  The 
paffage  of  the  ninth  pair. 

Fig.  3.  A View  of  the  External  furface  of  the 
Bafe  of  the  Skull. 

A,  The  two  dentes  incifores  of  the  right  fide. 
B,  The  dens  caninus.  C,  The  two  fmall  mo- 
lares.  D,  The  three  large  molares.  E,  The 
foramen  incifivum,  which  gives  paffage  to  fmall 
blood-veffels  and  neiwes.  F,  The  palate-plates 
of  the  offa  maxillaria  and  palati,  joined  by  the 
longitudinal  and  tranfverfe  palate  futures.  G, 
The  foramen  palatinum  pofterius,  for  the  pala- , 
tine  veffels  and  nerv^es.  H,  The  os  maxillare 

K 2 fuperius 


148  OSTEOLOGY.  Part  I. 

fuperms  of  the  right  fide.  I,  The  os  malas. 

K,  The  zygomatic  procefs  of  the  temporal  bone- 

L,  The  pollerior  extremity  of  the  offa  fpongiofa. 

M,  The  pofterior  extremity  of  the  vomer,  which 
forms  the  back-part  of  the  feptum  nafi.  N,  The 
pterygoid  procels  of  the  right  fide  of  the  fphenoid 
bone.  O O,  The  foramina  ovalia.  P P,  The 
foramina  fpinalia.  QjQ^  The  paffages  of  the 
internal  carotid  arteries.  R,  A hole  between 
the  point  of  each  pars  petrofa  and  cuneiform  pro- 
cefs of  the  occipital  bone,  which  is  hlled  up  with 
a ligamentous  fubftance  in  the  recent  fuhjedf.  S, 
The  paifage  of  the  left  lateral  fmus.  T,  The 
pofterior  condyloid  foramen  of  the  left  fide.  U, 
The  foramen  maftoideum.  V,  The  foramen 
magnum.  W„  The  inferior  orbitar  fiffure.  X, 
The  glenoid  cavity,  for  the  articulation  of  the 
lower  jaw.  Y,  The  fquamous  part  of  the  tem- 
poral bone.  Z,  The  maftoid  procefs,  at  the 
inner  fide  of  vriiich  is  a fofl'a  for  the  pofterior  bel- 
ly of  the  digaftric  mufcle.  a.  The  ftyloid  pro- 
cefs. b.  The  meatus  auditorius  externus.  c, 
The  left  condyle  of  the  occipital  bone,  d.  The 
perpendicular  occipital  fpine.  e e.  The  inferior 
horizontal  ridge  of  the  occipital  bone,  f f.  The 
fuperior  horizontal  ridge,  which  is  oppofite  to 
the  crucial  ridge  where  the  longitudinal  fmus  di- 
vides to  form  the  lateral  fmufes.  ggg?  The 
lambdoid  future,  h.  The  left  fquamous  future, 
i,  The  parietal  bone. 


Fig.  4. 


Part  L OSTEOLOGY.  149 

Fig.  4.  The  anterior  furface  of  the  Ossa  Nasi. 

A,  The  upper  part,  which  joins  the  os  frontis. 

B,  The  under  end,  which  joins  the  cartilage  of 
the  nofe.  C,  The  inner  edge,  where  they  join 
each  other. 

Fig.  5.  The  pofterior  furface  of  the  Ossa  Nasi. 

A A,  Their  cavity,  which  forms  part  of  the 
arch  of  the  nofe.  B B,  Their  ridge  or  fpine, 
which  projedfs  a little  to  be  fixed  to  the  fore-part 
of  the  feptum  narium. 

Fig.  6.  The  external  furface  of  the  Os  Maxil- 
LARE  SuPERius  of  the  left  fide. 

A,  The  nafal  procefs.  B,  The  orbitar  plate. 

C,  The  unequal  furface  which  joins  the  os  malse. 

D,  The  external  orbitar  hole.  E,  The  opening 
into  the  noftril.  F,  The  palate-plate.  G,  The 
maxillary  tuberofity.  H,  part  of  the  os  palati. 
I,  The  two  dentes  incifores.  K,  The  dens  ca- 
ninus.  L,  The  twm  fmall  dentes  molares.  M, 
The  three  large  dentes  molares. 

Fig.  7.  The  internal  furface  of  the  OsMaxil- 
LARE  SuPERius  and  Os  Palati. 

A,  The  nafal  procefs.  B B,  Eminences  for 
the  connedtion  of  the  os  fpongiofum  inferius. 
D,  The  under  end  of  the  lachrymal  groove.  E, 

The 


150  OSTEOLOGY.  Part  I. 

The  antrum  maxillare.  F,  The  nafal  fpine,  be- 
tween which  and  B is  the  cavity  of  the  noftril. 

The  palate-plate.  H,  The  orbitar  part  of 
the  os  palati.  I,  The  nafal  plate.  K,  The  fu- 
ture which  unites  the  maxillary  and  palate 
bones.  L,  The  pterygoid  procefs  of  the  palate 
bones. 

Fig.  8.  The  external  furface  of  the  right  Os 
Unguis. 

A,  The  orbitar  part.  B,  The  lachrymal  part. 

C,  The  ridge  between  them. 

Fig.  9.  The  internal  furface  of  the  right  Os 
Unguis. 

This  fide  of  the  bone  has  a furrow  oppofite  to 
the  external  ridge  ; all  behind  that  is  irregular, 
where  it  covers  part  of  the  ethmoidal  cells. 

Fi  G.  10.  The  external  furface  of  the  left  Os 
Mal^. 

A,  The  fuperior  orbitar  procefs.  B,  The 
inferior  orbitar  procefs.  C,  The  malar  procefs. 

D,  The  zygomatic  procefs.  E,  The  orbitar 
plate.  F,  A paffage  for  fmall  veffels  into  or  out 
of  the  orbit. 

Fig.  II.  The  internal  furface  of  the  left  Os 
M ALiE. 

A,  The  fuperior  orbitar  procefs.  B,  The  in- 
ferior 


f Part  I.  OSTEOLOGY.  151 

ferior  orbitar  procefs.  C,  The  malar  procefs. 

I D,  The  zygomatic  procefs.  E,  The  internal  or- 
' bitar  plate  or  procefs. 

Fig.  12.  The  external  furface  of  the  right  Os 
Spongiosum  Inferius. 

A,  The  anterior  part.  B,  The  hook-like  pro- 
cefs for  covering  part  of  the  antrum  maxillare. 
C,  A fmall  procefs  which  covers  part  of  the  un- 
[ der  end  of  the  lachrymal  groove.  D,  The  in- 
ferior edge  turned  a little  outwards. 

Fig.  13.  The  internal  furface  of  the  Os  Spon- 
giosum Inferius. 

A,  The  anterior  extremity.  B,  The  upper 
edge  which  joins  the  fuperior  maxillary  and  pa- 
late bones. 

Fig.  14.  The  pofterior  and  external  furface  of 
the  right  Os  Palati. 

A,  The  orbitar  procefs.  B,  The  nafal  lam- 
ella. C,  The  pterygoid  procefs.  D,  The  pa- 
late procefs. 

Fig.  15.  The  anterior  and  external  furface  of 
the  right  Os  Palati. 

A,  The  orbitar  procefs.  B,  An  opening 
through  which  the  lateral  nafal  velfgls  and  nerves 

pafs. 


152  OSTEOLOGY.  Part  I.  ! 

pafs.  C,  The  nafal  lamella.  D,  The  pterygoid  | 
procefs.  E,  The  pofterior  edge  of  the  palate  ’ 
procefs  for  the  connedion  of  the  velum  palati. 

F,  The  inner  edge  by  which  the  two  offa  palati  , 
are  connected. 

Fig.  i6.  The  right  fide  of  the  Vomer. 

A,  The  upper  edge  which  joins  the  nafal  lam- 
ella of  the  ethmoid  bone  and  the  middle  cartilage 
of  the  nofe.  B,  The  inferior  edge,  which  is 
conneded  to  the  fuperior  maxillary  and  palate 
bones.  C,  The  fuperior  and  pofterior  part 
which  receives  the  proceflus  azygos  of  the  fphe-  I 
noid  bone. 

Fig.  17.  The  Maxilla  Inferior. 

A,  The  chin.  B,  The  bafe  and  left  fide.  C, 
The  angle.  D,  Thecoronoid  procefs.  E,  The 
condyloid  procefs.  F,  The  beginning  of  the 
inferior  maxillary  canal  of  the  right  fide,  for 
the  entry  of  the  nerve  and  blood- veflels.  G, 
The  termination  of  the  left  canal.  H,  The 
two  dentes  incifores.  I,  The  dens  caninus.  K, 
The  two  fmall  molares.  L,  The  three  large  mo- 
lares. 

Fig.  18.  The  different  claftes  of  the  Teeth. 

I,  2,  A fore  and  back  view  of  the  two  ante- 
rior dentes  incifores  of  the  lov/er  jaw.  3,  4, 

Similar 


Part  I.  OSTEOLOGY.  153 

Similar  teeth  of  the  upper  jaw.  3,  6,  A fore 
and  back  view  of  the  dentes  canini.  y,  8,  The 
anterior  dentes  molares.  9,  10,  ii,  Thepofte- 
rior  dentes  molares.  12,  13,  14,  15,  16,  Un- 
ufual  appearances  in  the  fhape  and  fize  of  the 
teeth. 

Fig,  19.  The  external  furface  of  the  Os  Hy- 

OIDES. 

A,  The  body.  B B,  The  cornua.  C C,  The 
appendices. 

Plate  XXII. 

Fig.  I.  A Pofterior  View  of  the  Sternum  and 
Clavicles,  with  the  ligament  connecting 
the  clavicles  to  each  other. 

a,  The  pofterior  furface  of  the  fternum.  bb, 
The  broken  ends  of  the  clavicles,  c c c c,  The 
tubercles  near  the  extremity  of  each  clavicle,  d, 
The  ligament  connecting  the  clavicles. 

Fig.  3.  A Fore-view  of  the  Left  Scapula, 
and  of  a half  of  the  Clavicle,  with  their 
Ligaments. 

a.  The  fpine  of  the  fcapula.  b.  The  acro- 
mion. c.  The  inferior  angle,  d.  Inferior  cofta. 
e.  Cervix.  f.  Glenoid  cavity,  covered  with 
cartilage  for  the  arm-bone,  gg.  The  capfular 
ligament  of  the  joint,  h.  Coracoid  procefs.  i. 

The 


154  OSTEOLOGY.  PartL 

The  broken  end  of  the  clavicle,  k,  Its  extremity 
joined  to  the  acromion.  1,  A ligament  coming 
out  fmgle  from  the  acromion  to  the  coracoid  pro- 
cefs.  m,  A ligament  coming  out  fmgle  from  the 
acromion,  and  dividing  into  two,  which  are  fixed 
to  the  coracoid  procefs. 

Fig.  3.  The  Joint  of  the  Elbow  of  the  Left 
Arm,  with  the  Ligaments. 

a,  The  os  humeri,  b.  Its  internal  condyle, 
c c,  The  two  prominent  parts  of  its  trochlea  ap- 
pearing through  the  capfular  ligament,  d.  The  ! 
ulna,  e,  he  radius,  f.  The  part  of  the  liga- 
ment including  the  head  of  the  radius. 

Fig.  4.  The  Bones  of  the  Right-Hand,  with 

the  Palm  in  view.  I 

a.  The  radius,  b.  The  ulna,  c.  The  fcap-  j 

hold  bone  of  the  carpus,  d,  The  os  lunare.  \ 

e,  The  os  cuneiforme.  f,  The  os  pififorme.  g,  Ij 
Trapezium,  h,  Trapezoides.  i,  Capitatum.  k,  I 
unciforme.  1,  The  four  metacarpal  bones  of  ■ 
the  fingers,  m.  The  firfi:  phalanx,  n,  The  ' 
fecond  phalanx,  o.  The  third  phalanx,  p, 
The  metacarpal  bone  of  the  thumb,  q,  The 
firfi:  joint,  r.  The  fecond  joint. 

Fig.  5.  The  Pofterior  View  of  the  Bones  of  the 
Left-Hand. 

The  explication  of  Fig.  4.  ferves  for  this  fi- 
gure ; ; 


Part  I.  OSTEOLOGY.  155 

gure  ; the  fame  letters  pointing  out  the  fame 
bones,  though  in  a different  view. 

Fig.  6.  The  Upper  Extremity  of  the  Tibia, 
with  the  Semilunar  Cartilages  of  the  Joint  of 
the  Knee,  and  fome  Ligaments. 

a.  The  ftrong  ligament  which  connedts  the 
rotula  to  the  tubercle  of  the  tibia,  b b.  The 
parts  of  the  extremity  of  the  tibia,  covered  with 
cartilage,  which  appear  within  the  femilunar 
cartilages.  c c.  The  femilunar  cartilages,  d. 
The  two  parts  of  what  is  called  the  crofs  liga- 
ment. 

Fig.  y.  The  Pofterior  View  of  the  Joint  of  the 
Right-Knee. 

a.  The  os  femoris  cut.  b.  Its  internal  con- 
dyle. c.  Its  external  condyle,  d.  The  back- 
part  of  the  tibia,  e,  The  fuperior  extremity  of 
the  fibula,  f.  The  edge  of  the  internal  femilu- 
nar cartilage,  g.  An  oblique  ligament,  h,  A 
larger  perpendicular  ligament.  i,  A ligament 
connedting  the  femur  and  fibula. 

Fig.  8.  The  Anterior  View  of  the  Joint  of  the 
Right  Knee. 

b.  The  internal  condyle,  c.  Its  external  con- 
dyle. d.  The  part  of  the  os  femoris,  on  which 
the  patella  moves,  e,  A perpendicular  ligament. 

ff.  The 


156  OSTEOLOGY.  Part  I. 

f f,  The  two  parts  of  the  crucial  ligaments,  g g, 
The  edges  of  the  two  moveable  femilunar  carti- 
lages. h,  The  tibia,  i,  The  ftrong  ligament 
of  the  patella,  k,  The  back  part  of  it  where 
the  fat  has  been  dilfedted  away.  1,  The  exter- 
nal depreffion.  m,  The  internal  one.  n,  The 
cut  tibia. 

Fig.  9.  A View  of  the  inferior  part  of  the  Bones 
of  the  Right  Foot. 

a,  The  great  knob  of  the  os  calcis.  b,  A pro- 
minence on  its  outfide.  c,  The  hollow  for  the 
tendons,  nerves,  and  blood-veifels.  d,  The  an- 
terior extremity  of  the  os  calcis.  e.  Part  of  the 
ahragalus.  f,  Its  head  covered  with  cartilage. 

g,  The  internal  prominence  of  the  os  naviculare. 

h.  The  os  cuboides.  i.  The  os  cuneiforme  inter- 
num ; k, — Medium  ; — 1, — Externum,  m,  The 
metatarfal  bones  of  the  four  leffer  toes,  n,  The 
firft — o,  The  fecond — p.  The  third  phalanx 
of  the  four  leffer  toes,  q,  The  metatarfal  bones 
of  the  great  toe.  r,Its  firft — s,  Its  fecond  joint. 

Fig.  10.  The  Inferior  Surface  of  the  two  large 
Sesamoid  Bones,  at  the  firft  Joint  of  the 
Great  Toe. 

Fig.  II,  The  Superior  View  of  the  Bones  of 
the  Right  Foot. 

a,  b,  as  in  Fig.  9.  c.  The  fuperior  head  of 
the  aftragalus. — d,  as  in  Fig.  9, 


Fig.  12. 


PartI.  osteology.  157 

Fig.  12.  The  View  of  the  Sole  of  the  Foot, 
with  its  Ligaments. 

a,  The  great  knob  of  the  os  calcis.  b,  The 
hollow  for  the  tendons,  nerves,  and  blood-veffels. 
c.  The  {heaths  of  the  fiexores  pollicis  and  digi- 
torum  longi  opened,  d,  The  ftrong  cartilagin- 
ous ligament  fupporting  the  head  of  the  aftraga- 
lus.  e,  h,  T wo  ligaments  which  unite  into  one, 
and  are  fixed  to  the  metatarfal  bone  of  the  great 
toe.  f,  A ligament  from  the  knob  of  the  os  cal- 
cis to  the  metatarfal  bone  of  the  little  toe.  g,  A 
ftrong  triangular  ligament,  which  fuppoits  the 
bones  of  the  tarfus.  i,  The  ligaments  of  the 
joints  of  the  five  metatarfal  bones. 

Fig.  13.  a,  The  head  of  the  thigh  bone  of  a 
child,  b,  The  ligamentum  rotundum  connedf- 
ing  it  to  the  acetabulum,  c,  The  capfukir  liga- 
ment of  the  joint  with  its  arteries  injected,  d. 
The  numerous  veffels  of  the  mucilaginous  gland 
injedted. 

Fig.  14.  The  Back-view  of  the  Cartilages  of  the 
Larynx,  with  the  Os  Hyoides. 

a.  The  pofterior  part  of  the  bafe  of  the  os 
hyoides.  b b,  Its  cornua,  c.  The  appendix  of 
the  right  fide,  d,  A ligament  fent  out  from  the 
appendix  of  the  left  fide,  to  the  ftyloid  procefs 
of  the  temporal  bone,  e,  The  union  of  the 
bafe  with  the  left  cornu,  f f,  The  pofterior  Tides 

of 


15S  OF  THE  INTEGUMENTS  Part  IL 
of  (g)  the  thyroid  cartilage,  h h,  Its  fuperior 
cornua,  i i,  Its  inferior  cornua,  k,  The  cricoid 
cartilage.  1 1,  The  arytenoid  cartilages,  m,  The 
entry  into  the  lungs,  named  glottis,  n,  The 
epiglottis,  o o,  The  fuperior  cartilages  of  the 
trachea,  p,  Its  ligamentous  back  part. 

Fig.  15.  The  Superior  Concave  furface  of  the 
Sesamoid  Bones  at  the  firft  joint  of  the 
Great  Toe,  with  their  Ligaments. 

a.  Three  fefamoid  bones,  b.  The  ligament- 
ous fubftance  in  which  they  are  formed. 


Part  II. 

Of  the  soft  PARTS  in  General; 

0/' Common  Integuments,  luith  their  Appendagts  ■, 
And  of  the  Muscles. 

Anatomical  writers  ufually  proceed  to 
a defcription  of  the  mufcles  after  having 
finifhed  the  ofteology  ; but  we  Ihall  deviate  a 
little  from  the  common  method,  with  a view  to 
defcribe  every  thing  clearly  and  diftindtly,  and 
to  avoid  a tautology  which  would  otherwife  be 
unavoidable.  All  the  parts  of  the  body  are  fo 
intimately  conneded  with  each  other,  that  it 

feetns 


Plate  XXI 


TOM\r 


Part  II.  AND  MUSCXES.  159 

feems  inipoffible  to  convey  a juft  idea  of  any  one 
of  them,  without  being  in  foine  meafure  oblig- 
ed to  fay  foinething  of  others  ; and  on  this  ac- 
count we  wifti  to  mention  in  this  place  the  names 
and  fituation  of  the  principal  vifcera  of  the  body, 
that  when  mention  is  hereafter  made  of  any  one 
of  them  in  the  courfe  of  the  work,  the  reader 
may  at  leaft  know  where  they  are  placed. 

After  this  little  digreflion,  the  common  inte- 
guments, and  after  them  the  mufcles  will  be  de- 
fcribed ; we  then  propofe  to  enter  into  an  exa- 
mination of  the  feveral  vifcera  and  their  differ- 
ent functions.  In  defcribing  the  brain,  occafion 
will  be  taken  to  fpeak  of  the  nerves  and  animal 
fpirits.  The  circulation  of  the  blood  will  follow 
the  anatomy  of  the  heart,  and  the  fecretions  and 
other  matters  will  be  introduced  in  their  proper 
places. 

The  body  is  divided  into  three  great  cavi- 
ties. Of  thefe  the  uppermoft  is  formed  by  the 
bones  of  the  cranium,  and  inclofes  the  brain  and 
cerebellum. 

The  fecond  is  compofed  of  the  vertebrae  of 
the  back,  the  fternum,  and  true  ribs,  with  the  ad- 
ditional affiftance  of  mufcles,  membranes,  and 
common  integuments,  and  is  called  the  thorax — 
It  contains  the  heart  and  lungs. 

The  third,  and  inferior  cavity,  is  the  abdo- 
men. It  is  feparated  from  the  thorax  by  means 
of  the  diaphragm,  and  is  formed  by  the  lumbar 
vertebrae,  the  os  facrum,  the  offa  innominata, 

and 


i6o  OF  THE  INTEGUMENTS  Part  II, 
and  the  fade  ribs,  to  which  we  may  add  the  pe- 
ritonaEum,  and  a variety  of  mufcles.  This  ca- 
vity inclofes  the  ftomach,  inteftines,  omentum  or 
cawl,  liver,  pancreas,  fpleen,  kidneys,  urinary  , 
bladder,  and  parts  of  generation. 

Under  the  divifion  of  common  integuments 
are  ufually  included  the  epidermis,  or  fcarf-Ikin,  | 
the  reticulum  mucofum  of  Malpighi,  the  cutis  or 
true  fkin,  and  the  membrana  adipofa. — The  hair 
and  nails,  as  v^^ell  as  the  febaceous  glands  may 
be  confidered  as  appendages  to  the  fkin. 

Sect.  I.  Of  the  Skin. 

\ Of  the  ScARF^/;^. 

The  epidermis^  cuticula^  or  fcarffdn^  is  a 
•fine  tranfparent,  and  infenfible  pellicle,  deftitute 
of  nerves  and  blood-veffels,  which  invefts  the 
body,  and  everywhere  covers  the  true  fkin.  T his 
fcarf~fl?:in,  which  feems  to  be  very  fimple,  ap~  ' 
pears,  when  examined  with  a microfcope,  to  be 
compofed  of  feveral  laminas  or  fcales  which  are 
increafed  by  preffure,  as  we  may  obferve  in  the 
hands  and  feet,  where  it  is  frequently  much  I 
thickened,  and  becomes  perfedfly  callous.  It 
fe-ems  to  adhere  to  the  cutis  by  a number  of  very 
minute  filaments,  but  may  eafily  be  feparated 
from  it  by  heat,  or  by  maceration  in  water.  Some 
anatomical  writers  have  fuppofed  that  it  is  formed 
by  a moifture  exhaled  from  the  whole  furface  of 
I the 


Part  II.  AND  MUSCLES.  i6r 

the  body,  which  gradually  hardens  when  it 
comes  into  contad:  with  the  air.  They  were  per- 
haps induced  to  adopt  this  opinion,  by  obfendng 
the  fpeedy  regeneration  of  this  part  of  the  body 
when  it  has  been  by  any  means  deftroyed,  it  ap- 
pearing to  be  renewed  on  all  parts  of  the  furface 
at  the  fame  time ; whereas  other  parts  which  have 
been  injured,  are  found  to  dired  their  growth 
from  their  circumference  only  towards  their  cen- 
tre. But  a demonftrative  proof  that  the  epider- 
mis is  not  a fluid  hardened  by  means  of  the  ex- 
ternal air,  is  that  the  foetus  in  utero  is  f^und  to 
have  this  covering.  Lieuwenhoeck  fuppofed  its 
formation  to  be  owing  to  the  expanhon  of  the 
extremities  of  the  excretory  vefl'els  which  are 
found  every  where  upon  the  furface  of  the  true 
fkin.  Ruyfch  attributed  its  origin  to  the  nervous 
papilljE  of  the  flcin  ; and  Heifter  thinks  it  pro- 
bable, that  it  may  be  owing  both  to  the  papills 
and  the  excretory  veifels.  The  celebrated  Mor- 
gagni, on  the  other  hand,  contends  that  it  is 
nothing  more  than  the  furface  of  the  cutis,  har- 
dened and  rendered  infenfible  by  the  liquor  am- 
nii  in  utero,  and  by  the  prefTure  of  the  air.  This 
is  a fubjed,  hoM^'ever,  on  which  we  can  advance 
nothing  wdth  certainty. 

The  cuticle  is  pierced  with  an  inflnite  number 
of  pores  or  little  holes,  v/hich  afford  a paffage  to 
the  hairs,  fweat,  and  infenfible  perfpiration,  and 

L likewife 

* Adverfar.  Anar.  1 1 . Auimadver.  2. 


i62  of  the  integuments  Part  II. 

likewife  to  warm  water,  mercury,  and  whatever 
elfe  is  capable  of  being  taken  in  by  the  abforbents 
of  the  fkin.  The  lines  which  we  obferve  on 
the  epidermis  belong  to  the  true  fkin.  The  cu- 
ticle adjufts  itfelf  to  them,  but  does  not  form 
them. 

§ 2.  Of  the  Rete  Miicofum. 

Between  the  epidermis  and  cutis  we  meet 
with  an  appearance  to  which  Malpighi,  who 
firft  defcpibed  it,  gave  the  name  of  rete  mucofum^ 
fuppofmg  it  to  be  of  a membranous  ftrud;ure, 
and  pierced  with  an  infinite  number  of  pores  ; 
but  the  fail  is,  that  it  feems  to  be  nothing  more 
than  a mucous  fubftance  which  may  be  diflblved 
by  macerating  it  in  water,  while  the  cuticle  and 
cutis  preferve  their  texture. 

The  colour  of  the  body  is  found  to  depend  on 
the  colour  of  this  rete  mucofum  ; for  in  negroes 
it  is  obferved  to  be  perfedlly  black,  whilft  the 
true  fldn  is  of  the  ordinary  colour. 

The  blifters  which  raife  the  fkin  when  burnt 
or  fcalded,  have  been  fuppofed  by  fome  to  be 
owing  to  a rarefadtion  of  this  mucus  ; but  they 
are  more  probably  occafioned  by  an  increafed 
addon  of  the  veffels  of  the  part,  together  with 
an  afflux  and  effufion  of  the  thinner  parts  of  the 
blood 


§3-  Of 


Part  IL 


AND  MUSCLES.  . 


163 


§ 3*  Cutis,  or  True  Skin. 

The  cutis  is  compofed  of  fibres  clofely  com- 
padted  together,  as  we  may  obferve  in  leather, 
which  is  the  prepared  fkin  of  animals.  Thefe 
fibres  form  a thick  net-work,  which  every  where 
admits  the  filaments  of  nerves,  and  an  infinite 
number  of  blood-veffels  and  lymphatics. 

The  cutis,  when  the  epidermis  is  taken  off,  is 
found  to  have,  throughout  its  whole  furface,  in- 
numerable papillse,  which  appear  like  very  mi- 
nute granulations,  and  feem  to  be  calculated  to 
receive  the  impreffions  of  the  touch,  being  the 
moll  eafily  obferved  where  the  fenfe  of  feeling  is 
the  moft  delicate,  as  in  the  palms  of  the  hands 
and  on  the  fingers. 

Thefe  papillae  are  fuppofed  by  many  anatomi- 
cal writers  to  be  continuations  of  the  pulpy  fub- 
llance  of  nerves,  whofe  coats  have  terminated 
in  the  cellular  texture  of  the  fkin.  The  great 
fenfibility  of  thefe  papillse  evidently  proves  them 
to  be  exceedingly  nervous  ; but  furely  the  nerv- 
ous fibrillse  of  the  fkin  are  of  themfelves  fcarcely 
equal  to  the  formation  of  thefe  papillse,  and  it 
feems  to  be  more  probable  that  they  are  formed 
like  the  reft  of  the  cutis. 

Thefe  papillse  being  defcribed,  the  ufes  of  the 
epidermis  and  the  reticulum  mucofum  will  be 
more  eafily  underftood ; the  latter  ferving  to 
keep  them  conftantly  moift,  while  the  former 

L 2 protedls 


1 64  OF  THE  INTEGUMENTS  Part  II. 
protedls  them  from  the  external  air,  and  modifies 
their  too  great  fenfihility. 

§ 4.  Of  the  Glands  of  the  Skin. 

In  different  parts  of  the  body  we  meet,  with- 
in the  fubftance  of  the  flcin,  with  certain  glands 
or  follicles,  which  difcharge  a fat  and  oily  humor 
that  ferves  to  lubricate  and  foften  the  fkin.  When 
the  fluid  they  fecrete  has  acquired  a certain  de- 
gree of  thicknefs,  it  approaches  to  the  colour 
and  confiftence  of  fuet ; and  from  this  appearance 
they  have  derived  their  name  of fehaceous  glands. 
They  are  found  in  the  greateft  number  in  the 
nofe,  ear,  nipple,  axilla,  groin,  fcrotum,  vagina, 
and  prepuce, 

Befides  thefe  febaceous  glands,  we  read,  in 
anatomical  books,  of  others  that  are  defcribed 
as  fmall  fpherical  bodies  placed  in  all  parts  of  the 
fkin,  in  much  greater  abundance  than  thofe  juft 
now  mentioned,  and  named  miliary^  from  their 
fuppofed  refemblance  to  millet-feed.  Steno,  who 
firft  defcribed  thefe  glands,  and  Malpighi,  Ruyfch, 
V erheyen,  Winflow,  and  others,  who  have  adopt- 
ed his  opinions  on  this  fubje£t,  fpeak  of  them  as 
having  excretory  ducfts,  that  open  on  the  furface 
of  the  cuticle,  and  diftil  the  fweat  and  matter  of 
infenfible  perfpiration ; and  yet,  notwithftand- 
ing  the  pofitive  manner  in  which  thefe  pretend- 
ed glands  have  been  fpoken  of,  we  are  now  fuf- 

ficiently 


Part  II.  AND  MUSCLES.  165 

fidently  convinced  that  their  exiftence  is  altoge- 
ther imaginary. 

§ y.  Of  the  Insensible  Pcrfpiration  and 
Sweat. 

The  matter  of  infenfible  perfpiration,  or  in 
other  words,  the  fiibtile  vapour  that  is  continu- 
ally exhaling  from  the  furface  of  the  body,  is 
not  fecreted  by  any  particular  glands,  but  feems 
to  be  derived  wholly  from  the  extremities  of  the 
minute  arteries  that  are  every  where  difperfed 
through  the  fkin.  Thefe  exhaling  velfels  are 
eafily  demonftrated  in  the  dead  fubjed;,  by  throw- 
ing water  into  the  arteries  ; for  then  fmall  drops 
exude  from  ail  parts  of  the  fkin,  and  raife  up 
the  cuticle,  the  pores  of  which  are  clofed  by 
death  ; and  in  the  living  fubjed,  a looking-glaJs 
placed  againft  the  fldn,  is  foon  obfcured  by  the 
vapour.  Bidloo  fancied  he  had  difcovered  duds 
leading  from  the  cutis  to  the  cuticle,  and  tranf- 
mitting  this  fluid  ; but  in  this  he  was  miftaken. 

When  the  perfpiration  is  by  any  means  in- 
creafed,  and  feveral  drops  that  were  infenflble 
when  feparate,  are  united  together  and  condenf- 
ed  by  the  external  air,  they  form  upon  the  fkin 
fmall,  but  vifible,  drops  called  fweat  (n).  This 
particularly  happens  after  much  exercife,  or 
whatever  occafions  an  increafed  determination  of 

fluids 

(n)  Liemveiihoeck  afFerts  that  one  drop  of  fweat  is  formed 
by  the  conflux  of  fifteen  drops  of  perfpirable  vapour. 


1 66  OF  THE  INTEGUMENTS  Part  II. 
fluids  to  the  furface  of  the  body  ; a greater  quan- 
tity of  perfpirable  matter  being  in  fuch  cafes 
carried  through  the  palfages  that  are  deftined  to 
convey  it  off. 

It  has  been  difputed,  indeed,  whether  the  in- 
fenfible  perfpiration  and  fweat  are  to  be  confider- 
ed  as  one  and  the  fame  excretion,  differing  only  li 
in  degree  ; or  whether  they  are  two  diffindt  ex- 
cretions derived  from  different  fources.  In  fup- 
port  of  the  latter  opinion,  it  has  been  alledged, 
that  the  infenfible  perfpiration  is  agreeable  to  na- 
ture, and  effential  to  health,  whereas  fweat  may 
be  confidered  as  a fpecies  of  difeafe.  But  this 
argument  proves  nothing ; and  it  feems  probable, 
that  both  the  infenfible  vapour  and  the  fweat  arerj- 
exhaled  in  a fimilar  manner,  though  they  differ  li 
in  quantity,  and  probably  in  their  qualities  ; the 
former  being  more  limpid,  and  feemingly  lefs 
impregnated  with  falts  than  the  latter : at  any 
rate  we  may  confider  the  fkin  as  an  emundtory  , 
through  which  the  redundant  water,  and  fome- 
times  the  other  more  faline  parts  of  the  blood, 
are  carried  off.  But  the  infenfible  perfpiration 
is  not  confined  to  the  fkin  only — a great  part  of 
what  we  are  conftantly  throwing  off  in  this  way  | 
is  from  the  lungs.  The  quantity  of  fluid  exhal- 
ed from  the  human  body  by  this  infenfible  per 
fpiration  is  vei*y  confiderable.  Sandtorius  (o) 

an 

i 

(o)  The  infenfible  perfpiration  is  fometimes  diftinguifhed 
by  the  name  of  this  phyfician,  who  was  born  in  the  territo- 
ries 


Part  II.  AND  MUSCLES.  167 

an  Italian  phyfician,  who  indefatigably  pafled  a 
great  many  years  in  a feries  of  ftatical  experiments, 
demonftrated  long  ago  what  has  been  confirmed 
by  later  obfervations,  that  the  quantity  of  vapour 
exhaled  from  the  fkin  and  from  the  furface  of 
the  lungs,  amounts  nearly  to  5-8ths  of  the  ali- 
ment we  take  in.  So  that  if  in  the  warm  climate 
of  Italy  a perfon  eats  and  drinks  the  quantity  of 
eight  pounds  in  the  courfe  of  a day,  five  pounds 
of  it  will  pafs  off  by  infenfible  perfpiration,  while 
three  pounds  only  will  be  evacuated  by  ftool,  u- 
rine,  faliva,  &c.  But  in  countries  where  the 
degree  of  cold  is  greater  than  in  Italy,  the  quan- 
tity of  perfpired  matter  is  lefs ; in  fome  of  the 
more  northern  climates,  it  being  found  not  to 
equal  the  difcharge  by  urine.  It  is  likewife  ob- 
ferved  to  vary  according  to  the  feafon  of  the  year, 
and  according  to  the  conftitution,  age,  fex,  dif- 
eafes,  diet,  exercife,  palTions,  &c.  of  different 
people. 

From 

ries  of  Venice,  and  was  afterwards  a profefTor  in  the  nni- 
verficy  of  Padua.  After  effimating  the  aliment  he  took  in, 
and  the  fenfible  fecretions  and  difcharges,  he  was  enabled  to 
afcertain  with  great  accuracy  the  weight  or  quantity  of  in- 
fenlible  perfpiration  by  means  of  a ftatical  chair  which  he 
contrived  for  this  purpofe  ; and  from  his  experiments,  which 
were  conducted  with  great  induftry  and  patience,  he  was 
led  to  determine  what  kinds  of  folid  or  liquid  aliment  in- 
creafed  ordiminifhed  it.  From  thefe  experiments  he  form- 
ed a fyftem,  which  he  publifhed  at  Venice  in  .614,  in  the 
form  of  aphorifms,  under  the  title  of  “ Ars  de  Medicina 
Statica.” 


1 68  OF  THE  INTEGUMENTS  Part  II, 

From  what  has  been  faid  on  this  fubjed;,  it 
will  be  eafily  conceived,  that  this  evacuation  can- 
not be  either  much  increafed  or  diminifhed  in 
quantity  without  alFeding  the  health. 

The  perfpirable  matter  and  the  fweat  are  in 
fome  meafure  analogous  to  the  urine,  as  appears 
from  their  tafte  and  faline  nature  (p).  And  it  is 
w^orthy  of  ohfervation,  that  when  either  of  thefe 
fecretions  is  increafed  in  quantity,  the  other  is  di-^ 
minifhed  ; fo  that  they  who  perfpire  the  leaft, 
ufuaily  pafs  the  greateft  quantity  of  urine,  and 
vice  verfa. 

§ 6.  Of  the  Nai  ls. 

The  NAILS  are  of  a compad  texture,  hard 
and  tranfparent  like  horn.  Their  origin  is  ftili 
a fubjed  of  difpute.  Malpighi  fuppofed  them 
to  be  formed  by  a continuation  of  the  papillse 
of  the  Ikin  : Ludwig,  on  the  other  hand,  main- 
tained, that  they  were  compofed  of  the  extre- 
mities of  blood-veflels  and  nerves  ; both  thefe 
opinions  are  now  defen^edly  rejeded. 

They  feem  to  poffefs  many  properties  in  com- 
mon with  the  cuticle  ; like  it  they  are  neither 
vafcular  nor  fenfible,  and  when  the  cuticle  is  fe- 
parated  from  the  true  fkin  by  maceration  or 
other  means,  the  nails  come  away  with  it. 

They 

(p)  Minute  chryftals  have  been  obferved  to  fltoot  upon  the 
cloaths  of  men  who  work  in  glafs-houfes.  Haller  Elm. 
Phyf 


Part  II.  AND  MUSCLES.  i6g 

They  appear  to  be  compofed  of  different  lay- 
ers, of  unequal  fize,  applied  one  over  the  other. 
Each  layer  feems  to  be  formed  of  longitudinal 
fibres. 

In  each  nail  we  may  diftinguifh  three  parts, 
viz.  the  root,  the  body  or  middle,  and  the  extre- 
mity. The  root  is  a foft,  thin,  and  white  fub- 
ftance  terminating  in  the  form  of  a crefcent ; the 
epidermis  adheres  very  ftrongly  to  this  part ; 
the  body  of  the  nail  is  broader,  redder  and 
thicker,  and  the  extremity  is  of  ftill  greater  firm- 
nefs. 

The  nails  increafe  from  their  roots,  and  not 
from  their  upper  extremity. 

Their  principal  ufe  is  to  cover  and  defend  the 
ends  of  the  fingers  and  toes  from  external  in- 
jury. 

^ j.  Of  the  Hair. 

The  hairs,  which  from  their  being  general- 
ly known  do  not  feem  to  require  any  definition, 
arile  from  diftincl  capfules  or  bulbs  feated  in  the 
cellular  membrane  under  the  fkin  (cl)’  Some 

of 

(q^)  Malpighi,  and  after  him  the  celebrated  Ruyfch,  fup- 
pofed  the  hairs  to  be  continuations  of  nerves,  being  of  opi- 
nion that  they  originated  from  the  papillse  of  the  iTcin,  which 
they  confidered  as  nervous  ; and  as  a corroborating  proof 
of  what  they  advanced,  they  argued  the  pain  we  feci  in 
plucking  them  out ; but  later  anatomifts  feem  to  have  re- 
jefted  this  doftrine,  and  confider  the  hairs  as  particular  bo- 
dies,. not  arifing  from  the  papillse  (for  in  the  parts  where 
the  papillse  abound  moft  there  *re  no  hairs),  but  from  bulbs 
or  capfules,  which  are  peculiar  to  them. 


170  OF  THE  INTEGUMENTS  Part  II. 
of  thefe  bulbs  inclofe  feveral  hairs.  They  may 
be  obferved  at  the  roots  of  the  hairs  which  form 
the  beard  or  whifkers  of  a cat. 

The  hairs,  like  the  nails,  grow  only  from  be- 
low by  a regular  propulfion  from  the  root,  where 
they  receive  nourifhment.  Their  bulbs,  when 
viewed  with  a microfcope,  are  found  to  be  of 
various  fhapes.  In  the  head  and  fcrotum  they 
are  roundifh  ; in  the  eye-brows  they  are  oval ; 
in  the  other  parts  of  the  body  they  are  nearly 
of  a cylindrical  fhape.  Each  bulb  feems  to  con-  >- 
lift  of  two  membranes,  between  which  there  is  11 
a certain  quantity  of  moifture.  Within  the  bulb 
the  hair  feparates  into  three  or  four  fibrillse  ; the 
bodies  of  the  hairs,  which  are  the  parts  without 
the  fkin,  vary  in  foftnefs  and  colour  according 
to  the  difference  of  climate,  age,  or  tempera- 
ment of  the  body  (r). 

Their  general  ufe  in  the  body  does  not  feem 
to  be  abfolutely  determined  ; but  hairs  in  parti- 
cular parts,  as  on  the  eye-brows  and  eye-lids, 
are  deftined  for  particular  ufes,  which  will  be 
mentioned  when  thofe  parts  are  defcribed. 

§8.  Of 

(R)The  hairs  differ  likewlfe  from  each  other,  and  may  not 
be  improperly  divided  into  two  claffes  ; one  of  which  may  in- 
clude the  hair  of  the  head,  chin,  pubes,  and  axillae  ; and 
the  other,  the  fofter  hairs,  which  are  to  be  obferved  almoft 
every  where  on  the  furface  of  the  body. 


Part  II. 


AND  MUSCLES. 


171 

^S.  Of  the  Cellular  Membrane  and  Fat. 

Thb  cellular  Membrane  is  found  to  in- 
veft  the  moft  minute  fibres  we  are  able  to  trace  ; 
fo  that  by  modern  phyfiologifts,  it  is  very  pro- 
perly confidered  as  the  univerfal  connedling  me- 
dium of  every  part  of  the  body. 

It  is  compofed  of  an  infinite  number  of  mi- 
nute cells  united  together,  and  communicating 
with  each  other.  The  two  difeafes  peculiar  to 
this  membrane  are  proofs  of  fuch  a communica- 
tion ; for  in  the  emphyfcma  all  its  cells  are  filled 
with  air,  and  in  the  anafarca  they  are  univer- 
fally  diftended  with  water.  Befides  thefe  proofs 
of  communication  from  difeafe,  a familiar  in- 
ftance  of  it  may  be  obferved  amongft  butchers, 
who  ufually  puncture  this  membrane,  and  by 
inflating  it  with  air  add  to  the  good  appearance 
of  their  meat. 

The  cells  of  this  membrane  ferve  as  refer- 
voirs  to  the  oily  part  of  the  blood  or  iv?/,  which 
feems  to  be  depofited  in  them,  either  by  tranfu- 
dation  through  the  coats  of  the  arteries,  that  ra- 
mify through  thefe  cells,  or  by  particular  vef- 
fels,  continued  from  the  end  of  arteries.  Thefe 
cells  are  not  of  a glandular  ftrudture,  as  Malpi- 
ghi and  others  after  him  have  fiippofed.  The 
fat  is  abforbed  and  carried  back  into  the  fyftem 
by  the  lymphatics.  The  great  waflie  of  it  in 
many  difeafes,  particularly  in  the  confumption, 
is  a fufficient  proof  that  fuch  an  abforption  takes 
place.  The 


172  OF  THE  INTEGUMENTS  Part  II. 

The  fullnefs  and  fize  of  the  body  are  in  a 
great  meafure  proportioned  to  the  quantity  of 
fat  contained  in  the  cells  of  this  membrane. 

In  the  living  body  it  feems  to  be  a fluid  oil, 
which  concretes  after  death.  In  graminivorous 
animals,  it  is  found  to  be  of  a firmer  confiftence 
than  in  man. 

The  fat  is  confined  to  the  fkin  alone,  being 
met  with  every  where  in  the  interftices  of  muf- 
cles,  in  the  omentum,  about  the  kidneys,  at  the 
bafis  of  the  heart,  in  the  orbits,  &c. 

The  chief  ufes  of  the  fat  feem  to  be  to  afford 
moifture  to  all  the  parts  with  which  it  is  con- 
necTed  ; to  facilitate  the  adlion  of  the  mufcles  ; 
and  to  add  to  the  beauty  of  the  body,  by  making 
it  every  where  fmooth  and  equal. 

Sect.  II.  Of  the  Muscles. 

The  muscles  are  the  organs  of  motion.  The 
parts  that  are  ufually  included  under  this  name 
confift  of  diftind;  portions  of  flefh,  fufceptible' 
of  contraction  and  relaxation ; the  motions  of 
which,  in  a natural  and  healthy  ftate,  are  fub-i 
jed  to  the  will,  and  for  this  reafon  they  are  call4 
ed  voluntary  mufcles.  But  befides  thefe,  ther^ 
are  other  parts  of  the  body  that  owe  their  power 
of  contradion  to  their  mufcular  fibres ; thus] 
the  heart  is  of  a mufcular  texture,  forming  what; 
is  called  a hollow  miifcle  ; and  the  urinary  blad- 
der, fcomach,  inteftines,  &c.  are  enabled  to 
ad  upon  their  contents,  merely  becaufe  they  are 

provided 


Part  II.  AND  MUSCLES.  173 

provided  with  mufcular  fibres.  Thefe  are  called 
involuntary  mufcles,  becaufe  their  motions  are 
not  dependent  on  the  will.  The  mufcles  of  ref- 
piration,  being  in  fome  meafure  influenced  by 
the  will,  are  faid  to  have  a mixed  motion. 

The  names  by  which  the  voluntary  mufcks 
are  diftinguifhed,  are  founded  on  their  fize,  fi- 
gure, fituation,  ufe,  or  the  arrangement  of  their 
fibres,  or  their  origin  and  infertion.  But  be- 
fides  thefe  particular  diftindions,  there  are  cer- 
tain general  ones  that  require  to  be  noticed. 
Thus,  if  the  fibres  of  a miifcle  are  placed  pa- 
rallel to  each  other  in  a flraight  diredion,  they 
form  what  is  ftyled  a re^ilinear  mufcle  ; if  the 
fibres  crofs  and  interfed  each  other,  they  confti- 
Itute  a compound  mufcle  ; a radiated  one,  if  the 
ifibres  are  difpofed  in  the  manner  of  rays  ; or  a 
penniform  mufcle,  if,  like  the  plume  of  a pen, 
they  are  placed  obliquely  with  refped  to  the 
tendon. 

Mufcles  that  ad  in  oppofition  to  each  other, 
are  called  antagonijia ; thus  every  extenfor  or 
mufcle  has  a flexor  for  its  antagonifl;,  and  vice 
verfa.  Mufcles  that  concur  in  the  fame  adion 
are  ftyled  congeneres. 

The  mufcles  being  attached  to  the  bones,  the 
latter  may  be  confidered  as  levers  that  are  mov- 
ed in  different  diredions  by  the  contradion  of 
thofe  organs. 

The  end  of  a mufcle  which  adheres  to  the 
moft  fixed  part  is  ufually  called  the  origin^  and 

that 


1 


1 74  OF  THE  INTEGUMENTS  Part  II. 
that  which  adheres  to  the  more  moveable  part 
the  infertion^  of  the  mufcle. 

In  every  mufcle  we  may  diftingulfh  two  kinds 
of  fibres ; the  one  foft,  of  a red  colour,  fenfi- 
ble,  and  irritable,  called  JieJhy  fibres ; the  other 
of  a firmer  texture,  of  a white  gliftening  colour, 
infenfible  without  irritability  or  the  power  of 
contracting,  and  named  tendinous  fibres.  They 
are  occafionally  intermixed ; but  the  flefhy  fi- 
bres generally  prevail  in  the  belly  or  middle  part 
of  the  mufcle,  and  the  tendinous  ones  in  the  ex- 
tremities. If  thefe  tendinous  fibres  are  formed 
into  a round  {lender  chord,  they  form  what  is 
called  the  tetido?i  of  the  mufcle ; on  the  other 
hand,  if  they  are  fpread  into  a broad  flat  fur- 
face,  the  extremity  of  the  mufcle  is  ftyled  apo- 
neurofis. 

The  tendons  of  many  mufcles,  efpecially  when 
they  are  long  and  expofed  to  preflTure  or  friCtion 
in  the  grooves  formed  for  them  in  the  bones,  are 
furrounded  by  a tendinous  {heath  or  fafcla^  in 
which  we  fometimes  find  afmall  mucous  fac  or 
burja  miicofa^  which  obviates  any  inconvenience 
from  friction.  Sometimes  we  find  whole  muC- 
cles,  and  even  feveral  mufcles,  covered  by  a faf- 
cia  of  the  fame  kind,  that  affords  origin  to  ma- 
ny of  their  fibres,  dipping  down  between  them, 
adhering  to  the  ridges  of  the  bones,  and  thus 
preventing  them  from  fwelling  too  much  when 
in  action.  The  moft  remarkable  inftance  of 
fuch  a covering  is  the  fafcia  lata  of  the  the  thigh. 

Each 


Part  II.  AND  MUSCLES.  175 

Each  mufcle  is  inclofed  by  a thin  covering  of 
cellular  membrane,  which  has  been  fomctimes 
improperly  confidered  as  peculiar  to  the  mufcles, 
and  defcribed  under  the  name  of  propria  mem- 
brana  mufculofa.  This  cellular  covering  dips 
down  into  the  fubftance  of  .the  mufcle,  conned;- 
ing  and  furrounding  the  moft  minute  fibres  we 
are  able  to  demonftrate,  and  affording  a fupport 
to  their  veffels  and  nerves. 

Lieuwhenhock  fancied  he  had  difcovered,  by 
means  of  his  microfcope,  the  ultimate  divifion 
of  a mufcle,  and  that  he  could  point  out  the  fim- 
ple  fibre,  which  appeared  to  him  to  be  an  hun- 
dred times  lefs  than  a hair  ; but  he  was  after- 
wards convinced  how  much  he  was  miftaken  on 
this  fubjed,  and  candidly  acknowledged,  that 
what  he  had  taken  for  a fimple  fibre  was  in  fad 
a bundle  of  fibres. 

It  is  eafy  to  obferve  feveral  of  thefe  fafculi  or 
bundles  in  a piece  of  beef,  in  which,  from  the 
coarfenefs  of  its  texture,  they  are  very  evident. 

The  red  colour  which  fo  particularly  diftin- 
guifhes  the  mufcular  or  flefhy  parts  of  animals, 
is  owing  to  an  infinite  number  of  blood-veffels 
that  are  difperfed  through  their  fubftance.  When 
we  macerate  the  fibres  of  a mufcle  in  wa- 
ter, it  becomes  of  a white  colour  like  all  other 
parts  of  the  body  divefted  their  blood.  The 
blood-veffels  are  accompanied  by  nerves,  and 
they  are  both  diftributed  in  fuch  abundance  to 
thefe  parts,  that  in  endeavouring  to  trace  the 

coiu'fe 


176  OF  THE  INTEGUMENTS  Part  IL 
coiirfe  of  the  blood-veffels  in  a mufcle,  it  would 
appear  to  be  formed  altogether  by  their  ramifica- 
tions ; and  in  an  attempt  to  follow  the  branches 
of  its  nerves,  they  would  be  found  to  be  equal 
in  proportion. 

If  a mufcle  is  pricked  or  irritated,  it  imme- 
diately contradls.  This  is  called  its  irritable 
principle  ; and  this  irritability  is  to  be  confider- 
ed  as  the  chara£teriftic  of  mufcular  fibres,  and 
may  ferve  to  prove  their  exiftence  in  parts  that 
are  too  minute  to  be  examined  by  the  eye.  This 
power,  which  difpofes  the  mufcles  to  contract 
when  ftimulated,  independent  of  the  will,  is 
fuppofed  to  be  inherent  in  them ; and  is  there- 
fore named  vis  infita.  This  property  is  not  to 
be  confounded  with  elafticity,  which  the  mem- 
branes and  other  parts  of  the  body  pofl'efs  in  a 
greater  or  lefs  degree  in  common  with  the  muf- 
cles; nor  with  fenfibility,  for  the  heart  though 
the  moft  irritable,  feems  to  be  the  leaf!  fenfible 
of  any  of  the  mufcular  parts  of  the  body. 

After  a mufcular  fibre  has  contradled,  it  foon 
returns  to  a ftate  of  relaxation,  till  it  is  excited 
afrefh,  and  then  it  contracts  and  relaxes  again. 

W e may  likewife  produce  fuch  a contradlion, 
by  irritating  the  nerve  leading  to  a mufcle,  al- 
though the  nerve  itfelf  is  not  affedied. 

This  principle  is  found  to  be  greater  in  fmall 
than  in  large,  and  in  young  than  in  old,  ani- 
mals. 

In  the  voluntary  mufcles  thefe  effe(5ts  of  con- 
I tradlion 


Part  II.  AND  MUSCLES.  177 

tradion  and  relaxation  of  the  flefliy  fibres  are 
produced  in  obedience  to  the  will,  by  what  may 
be  called  the  vis  tiervofa^  a property  that  is  not 
to  be  confounded  with  the  vis  infita.  As  the 
exiftence  of  a vis  infita  different  from  a vis  ner- 
vea,  was  the  doftrine  taught  by  Dodfor  Haller 
in  his  Mem.  Phyf  but  is  at  prefent  called  in  quef- 
tion  by  feveral,  particularly  Dodfor  Monro,  we 
think  it  neceffary  to  give  a few  objedfions,  as  Ha- 
ted in  his  Obfervations  on  the  Nervous  Syftem  : 

Vis  Nervea.  “ The  chief  experiment  (fays 
the  Dodlor)  which  feems  to  have  led  Dr.  Hal- 
ier to  this  opinion,  is  the  well  known  one,  that 
;he  heart  and  other  mufcles,  after  being  detach- 
ed from  the  brain,  continue  to  adf  fpontaneoufly, 
pr  by  ftimuli  may  be  roufed  into  adfion  for  a 
fonfiderable  length  of  time  ; and  when  it  cannot 
i)e  alledged,  fays  Dr.  Haller,  that  the  nervous 
luid  is  by  the  mind,  or  otherwife,  impelled  into 
he  mufcle. 

“ That  in  this  inftance  we  cannot  compre- 
end  by  what  power  the  nervous  fluid  or  energy 
an  be  put  in  motion,  mufl;  perhaps  be  granted  : 
>ut  has  Dr.  Halier  given  a better  explanation  of 
le  manner  in  which  his  fuppofed  vis  infita  be- 
ames  adf ive  ? 

“ If  it  be  as  difficult  to  point  out  the  caufe  of 
le  adfion  of  the  vis  infita  as  that  of  the  adfion 
f the  vis  nervea,  the  admiflion  of  that  new 
Dwer,  inftead  of  relieving,  would  add  to  our 
i^rplexity. 


M 


« We 


178  OF  THE  INTEGUMENTS  Pa^t  II. 

“We  fhould  then  have  admitted,  that  two 
caufes  of  a different  nature  were  capable  of  pro- 
ducing exadtly  the  fame  effedt ; which  is  not  in 
general  agreeable  to  the  laws  of  nature. 

“ We  fhould  find  other  confequences  arife 
from  fuch  an  hypothefis,  which  tend  to  weaken 
the  credibility  of  it.  For  inftance,  if  in  a found 
animal  the  vis  nervea  alone  produces  the  contrac- 
tion of  the  mufcles,  we  will  afk  what  purpofe 
the  vis  infita  ferves  ? If  both  operate,  are  we  to 
fuppofe  that  the  vis  nervea,  impelled  by  the 
mind  or  living  principle,  gives  the  order,  which 
the  vis  infita  executes,  and  that  the  nerves  are 
the  internuntii ; and  fo  admit  two  wife  agents 
employed  in  every  the  moft  fimple  adtion  ? But 
inftead  of  fpeculating  farther,  let  us  learn  the  ef- 
fedt  of  experiments,  and  endeavour  from  thefe 
to  draw  plain  conclufions. 

“ I.  When  I poured  a folution  of  opium  in 
water  under  the  fkin  of  the  leg  of  a frog,  the  muf- 
cles, to  the  furface  of  which  it  was  applied,  were 
veiyfoon  deprived  of  the  power  of  contradtion. 
In  like  manner,  when  I poured  this  folution  in- 
to the  cavity  of  the  heart,  by  opening  the 
vena  cava,  the  heart  was  almoft  inftantly  de- 
prived of  its  power  of  motion,  whether  the  ex- 
periment was  performed  on  it  fixed  in  its  place,] 
or  cut  out  of  the  body. 

“ 2.  I opened  the  thorax  of  a living  frog ; and! 
then  tied  or  cut  its  aorta,  fo  as  to  put  a flop  to' 
the  circulation  of  its  blood. 


“ I then 


Part  II.  AND  MUSCLES.  179 

“ I then  opehed  the  veii'a  cava,  and'  poured 
the  foiution  of  opium  into  the  heart ; and  found 
not  only  that  this  organ  was  inftantly  deprived 
of  its  powers  of  ad:ion,  but  that  in  a few  mi- 
nutes the  moft  diftant  mufcles  of  the  limbs  were 
extremely  weakened.  Yet  this  weaknefs  waa 
not  owing  to  want  of  circulation,  for  the  frog 
could  jump  about  for  more  than  an  hour  after 
the  heart  was  cut  out. 

“ In'  the  firft  of  thefe  two  experiments,  we 
obferved  the  fuppofed  vis  infita  deftroyed  by  the 
opium ; in  the  latter,  the  vis  nefvea  ; for  it  is 
evident  that  the  limbs  were  affected  by  the  fym- 
pathy  of  the  brain,  and  of  the  nervous  fyftem 
in  general,  with  the  nerves  of  the  heart. 

“ 3.  When  the  nerve  of  any  mufcle  is  firft 
divided  by  a ttanfverfe  fe£tion,  and  then  burnt 
with  a hot  iron,  or  punctured  with  a needle, 
the  mufcle  in  which  it  terminates  contracts  vio- 
lently, exadtly  in  the  fame  manner  as  when  the 
irritation  is  applied  to  the  fibres  of  the  mufele. 
But  when  the  hot  iron,  or  needle,  is  confined 
to  the  nerve.  Dr.  Haller  himfelf  muft  have  ad- 
mitted, that  this  vis  nervea,  and  not  the  vis  in- 
fita, was  excited!  But  here  I would  afk  two 
queftions. 

“ Firft,  Whether  we  do  not  as  well  under- 
hand how  the  vis  nervea  is  excited  when  irrita- 
tion is  applied  to  the  mufcle  as  when  it  is  appli- 
ed to  the  trunk'  of  the  nerve,  the  impelling 
M 2 power 


i8o  OF  THE  INTEGUMENTS  Part  II. 
power  of  the  mind  feeming  to  be  equally  want- 
ing in  both  cafes  ? 

“ Secondly,  If  it  appears  that  irritation  ap- 
plied to  the  trunk  of  a nerve  excites  the  vis  ner- 
vca,  why  fhould  we  doubt  that  it  can  equally 
well  excite  it  when  applied  to  the  fmall  and  ve- 
ry fenlible  branches  and  terminations  of  the  ne?;ye 
in  the  mufcle  ? \ 

“ As,  therefore,  it  appears  that  the  fuppofe^ 
vis  infita  is  deftroyed  or  excited  by  the  fame 
means  as  the  vis  nervea ; nay,  that  when,  by 
the  application  of  the  opium  to  the  heart  of  a frog, 
after  the  aorta  is  cut  and  the  circulation  in- 
terrupted, we  have  deftroyed  the  vis  infita,  the 
vis  nervea  is  fo  much  extinguiftied,  that  the 
animal  cannot  adt  with  the  diftant  mufcles  of  the 
limb ; and  that  thefe  afterward  grow  very  tor- 
pid, or  lofe  much  of  their  fuppofed  vis  infita  ; 
it  feems  clearly  to  follow,  that  there  is  no  juft 
ground  for  fuppofmg  that  any  other  principle 
produces  the  contraftion  of  a mufcle.” 

The  vis  nervofa^  or  operation  of  the  mind,  if 
w^e  may  fo  call  it,  by  which  a mufcle  is  brought 
into  contradion,  is  not  inherent  in  the  mufcle 
like  the  vis  mfita  j neither  is  it  perpetual,  like 
this  latter  property.  After  long  continued  or 
violent  exercife,  for  example,  the  voluntary 
mufcles  become  painful,  and  at  length  incapa- 
ble of  further  adion ; whereas  the  heart  and 
other  involuntary  mufcles,  the  motions  of  which  1 
depend  folely  on  the  vis  infita^  continue  through  a 

life  * 


Part  II.  AND  MUSCLES.  i8i 

life  in  a conftant  ftate  of  adion,  without  any 
inconvenience  or  wafte  of  this  inherent  principle. 

The  adion  of  the  vis  nervofa  on  the  volun- 
tary mufcles,  conftitutes  what  is  called  miifcidar  - 
motion ; a fubjed  that  has  given  rife  to  a variety 
of  hypothefes,  many  of  them  ingenious,  but 
none  of  them  latisfadory. 

Borelli  and  fome  others  have  undertaken  to 
explain  the  caufe  of  contradion,  by  fuppofmg 
that  every  mufcular  fibre  forms  as  it  were  a chain 
of  very  minute  bladders,  while  the  nerves  which 
are  diftributed  through  the  mufcle,  bring  with 
them  a fiipply  to  animal  fpirits,  which  at  our 
will  fill  thefe  bladders,  and  by  increafing  their 
diameter  in  width,  fhorten  them,  and  of  courfe 
the  whole  fibre. 

Borelli  fuppofes  thefe  bladders  to  be  of  a 
rhomboidal  Ihape  ; Bernouilli  on  the  other  hand 
contends  that  they  are  oval.  Our  countryman, 
Cowper,  fancied  he  had  filled  them  wfith  mer- 
cury ; the  caufe  of  this  miftake  was  probably 
owing  to  the  mercury’s  infinuating  itfelf  into 
fome  of  the  lymphatic  velTels.  The  late  inge- 
nius Mr.  Elliot  undertook  to  account  for  the  phe- 
nomena of  mufcular  motion  on  principles  very 
different  from  thofe  juft  now  mentioned.  He 
fuppofed  that  a deplogifticated  ftate  of  the  blood 
is  requifite  for  mufcular  adion,  and  that  a com- 
munication of  phlogifton  to  the  blood  is  a necef- 
fary  effed  of  fuch  adion. 

We  know  that  the  mufcular  fibre  is  Ihorten- 

ed, 


iSs  OF  THE  INTEGUMENTS,  &c.  Part  II. 
ed,  and  that  the  mufcle  itfelf  fwells  when  in 
adion  : but  how  thefe  phenomena  are  produced^ 
we  are  unable  to  determine.  We  likewife  know 
that  the  nerves  are  eflential  to  piufculaj*  motion  ; 
for  upon  dividing  or  making  a ligature  round 
the  nerve  leading  to  ^ mufcle,  the  latter  beconie§ 
incapable  of  motion.  A ligature  made  on  the 
artery  of  a mufcle  produces  a fimilar  effe<T ; a 
proof  this,  that  a regular  fupply  of  blood  is  alfo 
equally  necelfary  to  mulcular  motion.  The 
caufe  of  palfy  is  ufually  not  to  be  fought  for  in 
the  mufcle  affefted,  but  in  the  nerve  leading  to 
that  mufcle,  or  in  that  par|:  of  the  brain  or  fpir 
nal  marrow  from  vv'hich  the  nerve  4erives  itf 
origin. 


Of  the  pqrticulfir  Mufcles. 

As  the  enun]ieration  and  defcnption  of  the^ 
the  particular  mufcles  mull  be  dry  apd  uninter- J| 
taining  to  the  generality  of  readprs,  yet  canppt^f 
be  altogether  ofnitted  in  q wprk  pf  this  nature,  it 
appeared  eligible  to  j;hrow  this  part  of  the  fubr- 
jedt  into  the  form  of  a table  ; in  which  the 
name,  origin,  infertion,  an<l  pripcipal  ufe  of 
each  mufcle,  will  be  found  defcribed  ip  few  words, 
and  occafionally  its  etypiology  when  it  is  of 
Greek  derivation  or  difficult  to  be  pnderftood. 


A TABLED 


A TABLE  of  the  MUSCLES  arranged  according  to  their  Situation. 

[N.  B.  This  table  does  not  inelude  all  the  mufcles  of  the  body  ; thofe  belonging  to  the  eyes,  internal  ear,  inteftinum  rc(5timi, 
and  the  male  and  female  organs  of  generation,  being  defcribed  in  other  parts  of  the  work.  The  reader  will  bo  pleafed  to 
obferve  likewife,  that  although  all  the  mufeles  (a  few  only  excepted)  are  in  pairs,  mention  is  here  made  only  of  the  mufcles 
of  one  fide.] 


Part  II. 


A TABLE  OF  the  MUSCLES.  183 


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Part  II.  A TABLT  of  the  MUSCLES.  185 


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(h)  The  few  fibres  that  arife  from  the  Euftachian  tube  are  defcribed  as  a diftinft  mufcle  by  Albinus,  under  the  name  _, 
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Part  n.  A TABLE  of  MtJSCLES.  19^ 


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198  A TABLE  op  THE  MUSCLES.  Part  II. 


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^s)  The  tendon  formed  by  the  upper  ^ar  part  of  this  mufcle  in  its  way  to  the  linca  alba  is  divided  into  two  layers.  The 
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kribed  as  the  cremafier  mufcle. 


200  A TABLE  of  the  MUSCLES.  Part  II. 


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(1)  According  to  fome  writers,  this  mufcle  has  gotten  its  name  from  its  refemblance  to  the  fpleen  ; others  derive  Lt 
from  fpenium  fplint. 

(g)  So  named  on  account  of  ite  complicated  ftrufture. 

(h)  So  named  from  its  origin  from  the  neck  (Tfa;;^»^cl(c)  and  its  infertion  into  the  maftoid  procefs. 


3o6  a table  of  the  muscles.  Part  II. 


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1}  Several  thin  fafciculi  of  flefliy  fibres  arife  from  the  lower  ribs,  and  terminate  in  the  inner  fide  of  this  mufde.  Steno 
names  them  mafadi  ad  facm  kimkatem  acceffori'i.  The  facro-lumbalis  likewife  fends  off  a flethy  flip  from  its  upper  part, 
which  by  Douglas  and  Albinus  is  defcribed  as  a difiin^l  nuifclei  under  the  name  of  cervicalis  defcendensx  Morgagni  has 
very  properlyppnfidered  it  as  a part  of  the  (acro-lumbaib. 


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v8  A TABLE  of  the  MUSCLES.  Part  II. 


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Part  II.  A TABLE  of  the  MUSCLES.  219 


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ments,  os  facrum, 
and  os  coccygis. 

The  tldrd  mterofTeus  internus  (for  there  are  four  of  the  exterai  and  three  of  the  interni)  differs  from  the  reft  in 
rLing  the  middle  finger  from  the  thumb.  (c)  From  qcA^toc,  naies. 


220  A TABLE  QF  THE  MUSCLES,  P^rt  II. 


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So  named  from  its  pear-Ufce  fliape. 

The  two  portions  of  this  naufcle. having  been  defcribed  as  two  diftindl:  mufcles 'by  fonri’e  anatonaifts,  have  'occafioned 
named  n-effw/z/.  The  tcndon^of  the  obturator  intcrnus  runs  between  thefc  two  portions. 


Part  II.  A TABLE  of  the  MUSCLES. 


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(g)  The  iTuifcles  of  the  leg  and  thigh  are  covered  by  a broad  tendinous  membrane  called  fafcia  lata-,  that  furroiinds 

ll«em  in  the  manner  of  a Ihcath  It  is  lent  off  from, the  tendons  of  tlie  glutaei  and  other  mufcles,  and  dipping  down  be- 
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on  the  leg.  It  is  thickefl  on  the  infide  of  the  thigh.  ' 

(h)  The  tendon  of  this  muhie  fonj>s  the  outer- ham -J1  ring. 


222  A TABLE  OF  THE  MUSCLES*  Part  IL 


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bone  of  all  the  toes 


226  A TABLE  OF  THE  MUSCLES,  Part  IL 


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Part  il.  A TABLE  of  the  MUSCLES.  229 


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rfit).  Interoffei  pedis  Situated  between  the 
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ni(u). 


230  A TABLE  OF  THE  MUSCLES. 


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Part  II 


I PahtH.  of  the  muscles.  £3j 

EXPLANATION  op  PI.ATES  XXIII  and  XXIV. 
Plate  XXIII. 

Fig.  I.  The  Muscles  immediately  under 
the  common  teguments  on  the  anterior  part  of 
the  body  are  reprefented  on  the  right  fide ; and 
on  the  left  fide  the  Muscles  are  feen  which 
eome  in  view  when  the  exterior  ones  are  taken 
away. 

A,  The  frontal  mufcle.  B,  The  tendinous 
aponeurofis  which  joins  it  to  the  occipital ; hence 
both  named  occipito-frontalis.  C,  Attolens  au- 
rem.  D,  The  ear.  E,  Anterior  auris.  F F, 
Orbicularis  palpebrarum.  G.  Levator  labii  fu- 
perioris  alseque  nafu  H,  Levator  anguli  oris. 
I,  Zygomaticus  minor.  K,  Zygomaticus  ma- 
jor. L,  Maffater.  M,  Orbicularis  oris.  N, 
DeprelTor  labii  inferioris.  O,  DeprelTor  anguli 
oris.  P,  Buccinator.  Qj^>  Platyfma  myoides. 
R R,  Sterno-cleido-maftoidaeus.  S,  Part  of  the 
trapezius,  T,  Part  of  the  fcaleni. 

Superior  Extremity. — U,  Deltoides.  V, 
Pedloralis  major.  W,  Part  of  the  latiffimus  dor- 
fi.  X X,  Biceps  flexor  cubiti.  Y Y,  Part  of 
the  brachialis  externus.  Z Z,  The  beginning  of 
the  tendinous  aponeurofis  (from  the  biceps), 
which  is  fpread  over  the  mufcles  of  the  fore-arm. 
a a,  Its  ftrong  tendon  inferted  into  the  tubercle 
of  the  radius,  b b,  Part  of  the  brachialis  inter- 
nus.  c,  Pronator  radii  teres,  d,  Flexor  carpi 

radialis. 


232  OF  THE  MUSCLES.  Part  IT. 

radialis.  e,  Part  of  the  flexor  carpi  ulnaris.  f, 
Palmaris  longus.  g,  Aponeurofis  palmaris.  3, 
Palmaris  brevis,  i , Ligamentiim  carpi  annulare. 

2 2,  Abduttor  minimi  digiti.  h,  Supinator  radii  l 
longus.  i,  The  tendons  of  the  thumb,  k,  Ab-^, 
dudtor  pollicis.  I,  Flexor  pollicis  longus.  m m,-^| 
The  tendons  of  the  flexor  fnblimis  perforatus,* 
profundus  perforans,  and  lumbricales.— The 
Iheaths  are  entire  in  the  right  hand, — in  the  left 
cut  open  to  fhow  the  tendons  of  the  flexor  pro- 
fundus perforating  the  fublimis. 

Muscles  not  referred  to — in  the  left  fuperior 
extremity.— n,  Pedloralis  minoi^  leu  ferratus  an- 
ticus  minor,  o,  The  two  heads  of  (x  x)  the  i 
biceps,  p,  Coraco-brachialis.  q The  long  | 

head  of  the  triceps  extenfor  cubiti.  rr,  Teres  j 
major,  ff,  Subfcapularis.  1 1,  ■ Extenfores  ra- 
diales,  u,  Supinator  brevis,  v,  The  cut  extre-  i 
mity  of  the  pronator  teres,  w,  Flexor  fublimis 
perforatus.  x,  Part  of  the  flexor  profundus-,  y,  | 
Flexor  pollicis  longus.  z,  Part  of  the  flexor  pol- 
licis brevis.  4,  Abdu£tor  minimi  digiti.  5,  The 
four  lumbricales-. 

Trunk.' — 6,  Serrated  extremities  of  the  fer- 
ratus  anticus  major,  y y,  Obliquus  externus  ab- 
dominis. 8 8,  The  linea  alba.  9,  T he  umbi- 
licus. I o,  Pyramidalis.  1 1 1 1 , The  fperma- 
tic  cord.  On  the  left  fide  it  is  covered  by  the 
cremafter.  12  12,  Redtus  abdominis.  13, 
Obliquus  internus.  14  14,  &c.  Intercolfal 
mulcles. 


Inferior 


Part  II.  OF  THE  MUSCLES.  233 

Inferior  Extremities. — aa^  The  gra- 
cilis. h Parts  of  the  triceps,  c c,  Pedialis. 
d d,  Pfoas  magnus.  e e.  Iliacus  internus. 

Part  of  the  gluteus  medius.  Part  of  the  glu- 

tEEUs  minimus.  /?,  Cut  extremity  of  the  redus 
cruris,  i Vaftus  externus.  Tendon  of  the 
redus  cruris.  //,  Vaftus  internus.  Sartorius 
mufcle.  Fldhy  origin  of  the  tenfor  vaginse 

faemoris  or  membranoftis.  Its  tendinous  apo- 
neurofis  covers  (i),  the  vaftus  externus  in  the 
right  fide,  m vv,  Patella,  n Ligament  or 
tendon  from  it  to  the  tibia.  0,  Redus  cruris. 
/»,  Crura:  us.  q The  tibia,  r r,  Part  of  the 
Gemellus  or  gaftrocnemius  externus.*  fff^  Part 
of  the  foleus  or  gaftrocnemius  internus.  /,  Tibi- 
alis anticus.  ?/,  Tibialis  pofticus.  v Peronsi 
mufcles.  w ‘lu,  Extenfor  longus  digitoriim  pe- 
dis. X X,  Extenfor  longus  pollicis  pedis,  y,  Ab-r 
dudor  pollicis  pedis. 

Fig.  2.  The  Muscles,  Glands,  &c.  of  the 
Left  Side  of  the  face  and  neck,  after  the  com- 
mon Teguments  and  Piatyfma  myoides  have 
been  taken  off. 

a,  The  frontal  mufcle.  b,  Temporalis  and 
temporal  artery.  c,  Orbicularis  palpebrarum, 
d,  Levator  labii  fuperioris  alasque  nafi.  e,  Le- 
vator anguli  oris,  f,  Zygomaticus.  g,  Depreftbr 
labii  inferioris.  h,  Depreftbr  anguli  oris,  i,  Buc- 
cinator. k,  Maffeter.  1 1,  Parotid  gland,  m,  Its 

dud. 


234.  OF  the  muscles.  Part  II. 

n,  Sterno-deido-maftoidseus.  o.  Part  of 
the  trapezius,  p,  Sterno-hyoidsus.  q,  Sterno 
thyroidsus.  r,  Omo-hyoldasus.  f,  Levator 
fcapulse.  1 1,  Scaleni.  u,  Part  of  the  fplenius. 

J 

Fig.  3.  The  Muscles  of  the  Face  and  Neck  inj 

view  after  the  exterior  ones  are  taken  away. 

a a,  Corrugator  fupercilii.  b,  Temporalis,  c, 
Tendon  of  the  levator  palpebrse  fuperioris.  d,^ 
Tendon  of  the  orbicularis  palpebrarum,  e,  Maf-T 
feter.  f,  Buccinator,  g,  Levator  anguli  oris,^ 
h,  Deprellbr  labii  fuperioris  alseque  nafi.  i,  Or-  ' 
bicularis  oris,  k,  Depreffor  anguli  oris.  1,  Muf-^ 
•cles  of  the  os  hyoides.  m,  Sterno-cleido-mafto-j, , 
idseus.  ^ ; 

Fig.  4.  Some  of  the  Muscles  of  the  Os  Ffy-^ 
oides  and  Submaxillary  Gland.  1 

a,  Pait  of  the  malTeter  mufcle.  b,  Pofterior  * 
head  of  the  digraftic.  c,  Its  anterior  head,  dd,  * 
Sterno-hyoidseus.  e,  Omo-hyoidaeus.  f,  Stylo-  ‘ 
hyoidaeus.  g,  Submaxillary  gland  in  fitu. 

I 

Fig.  5.  The  fubmaxillar)^  Gland  and  Dud.  ! 

a,  Mufculus  mylo-hyoidaeus.  b.  Hyo-glof-  , 
fus.  c,  Submaxillary  gland  extra  fitu.  d,  Its 
dud.  i 


Plate 


1 ART  II. 


OF  THE  MUSCLES.  235 

Plate  XXIV. 

I Fig.  I.  The  muscles  immediately  under 
le  common  teguments  on  the  pofterior  part  of 
i le  body,  are  reprefented  in  the  right  fide  ; and 
n the  left  fide  the  Muscles  are  feen  which 
ome  in  view  when  the  exterior  ones  are  taken 
way. 

Head. — A A,  Occipito-frontalis.  B,  At- 
ollens  aurem.  C,  Part  of  the  orbicularis  pal- 
lebrarum.  D,  MalTeter.  E,  Pterygoidseus  in- 
ernus. 

Trunk. — Right  fide.  FFF,  Trapezius  feu 
ucullaris.  GGGG,  Latiffimus  dorfi.  H,Part 
)f  the  obliquus  externus  abdominis, 
i Trunk. — Left  fide.  I,  Splenius.  K,  Part 
)f  the  complexus.  L,  Levator  fcapulse.  M, 
Ihomboides.  NN,  Serratus  pofticus  inferior. 
3,  Part  of  the  longiffimus  dorfi.  P,  Part  of  the 
acro-lumbalis.  Part  of  the  femi-fpinalis 

lorfr.  R,  Part  of  the  ferratus  anticus  major.  S, 
Part  of  the  obliquus  internus  abdominis. 

Superior  Extremity. — Right  fide.  T, 
Deltoides.  U,  Triceps  extenforcubiti.  V,  Sur- 
pinator  longus.  W W,  Extenfores  carpi  radia- 
lis  longior  and  brevior.  X X,  Extenfor  carpi 
ulnaris.  Y Y,  Extenfor  digitorum  communis. 
Z,  Abdudtor  indicis.  123,  Extenfores  pol^ 
licis. 

Superior  Extremity. — ^Leftfide.  a,  Su- 
pra fpinatus.  b,  Infra-fpinatus.  c,  Teres  mi- 


236  OF  THE  MUSCLES.  Part  1 1 

nor  d,  Teres  major,  e,  Triceps  extenfor  cu 
biti.  f i,  Extenfores  carpi  radiales.  g,  Supi  c 
nator  brevis,  h,  Indicator,  i 2 3,  Extenfore 
pollicis,  i,  Abdudtor  minimi  digiti.  k,  Inter  i 
oflei.  ' : 

Inferior  Extremity. — Right  fide.  i| 
Gliitsens  maximus.  m,  Part  of  the  Glut:su 
iTtedius.  n,  Tenfor  vagina  femoris.  o,  Graci 
-lis.  p p.  Abductor  femoris  magniis.  q.  Par 
of  the  vahus  interniis.  r,  Semimembranofuf 
s,  Semitendinofus.  t,  Long  head  of  the  bicep  = 
flexor  cruris,  u u,  Gaftrocnemius  exteriius  fei 
gemellus,  v,  Tendo  Achillis.  w,  Soleus  fer 
gaftrocnemius  internus.  x x,  Peronsus  longd  1 
and  brevis,  y,  Tendons  of  the  flexor  longus  diga 
toriim  pedis  — -and  under  them  * flexor  brevis  ^ ! 
gitorum  pedis,  z,  Abdudior  minimi  digiti  pediS 
Inferior  Extremity.  Left  fide,  niyii 
!?,  r,  r,  j,  js,  Point  the  faiiii 

parts  as  in  the  right  flde.  n,  Pyriformis.  h h, 
Gemini,  c r,  Obturator  internus.  Quadra 
tus  femoris.  e>,  Coccygseus.  The  Ihort  heat 
of  the  biceps  flexor  cruris,  g Plaiitaris.  h 
Poplita^us.  Flexor  longus  pollicis  pedis. 

Fig.  2.  The  Palm  of  the  Left  Fland  after  th< 
common  Teguments  are  removed,  to  IhoVi 
the  Muscles  of  the  Fingers, 
a,  Tendon  of  the  flexor  caipii  radialis.  b 
Tendon  of  the  flexor  carpi  ulnaris.  c,  Tendon! 
of  the  flexor  fublimis  perforatus,  profundus  pen 

forani 


A ]Ni  AT  OMT. 


Anatomy 

CY  , IL 


[ at  II.  OF  THE  MUSCLES.  237 

f-rans  and  lumbricales.  d,  Abductor  pollicis. 
e?,  Flexor  pollicis  longus.  f,  Flexor  pollicis 
hevis.  g,  Palmaris  brevis,  h,  Abdudor  mi- 
rmi  digiti.  i,  Ligamentum  carpi  annulare,  k, 
t probe  put  under  the  tendons  of  the  flexor  di- 
j[orum  lublimis  ; which  are  perforated  by  1,  the 
f xor  digitorum  profundus,  m m m m,  Lum- 
licales.  n,  Abdudor  pollicis. 

] G.  3.  A Fore -view  of  tne  foot  and  Tendons  of 
the  Flexores  Digitorum. 
a,  Cut  extremity  of  the  tendo  Achillis.  b, 
Ipper  part  of  the  aflragalus.  c,  Os  calcis.  d, 
’endon  of  the  tibialis  anticus.  e,  Tendon  of 
le  extenfor  pollicis  longus.  f,  Tendon  of  the 
]*ronseus  brevis,  g,  Tendons  of  the  flexor  di- 
' torum  longus,  with  the  nonus  Vefalii.  h h, 
'he  whole  of  the  flexor  digitorum  brevis. 

Fig.  4.  Muscles  of  the  Anus, 
a a,  An  out  line  of  the  buttocks,  and  upper 
art  of  the  thighs,  b.  The  teftes  contained  in 
le  fcrotum.  c c,  Sphinder  ani.  d.  Anus,  e, 
.evator  ani.  f f,  Eredor  penis,  g g,  Accele- 
itor  urinsE.  h,  Corpus  cavernofum  urethra?. 

Fig.  5.  Muscles  of  the  Penis, 
a a,  b,  d,  e e,  f f,  h,  point  the  fame  as  in  fig. 
u c,  Sphinder  ani.  g g,  Tranfverfalis  penis. 


PART 


238 


OF  THE  ABDOMEN.  Part  I] 


Part  III. 

Of  the  abdomen,  or  LOWER  BELLY. 
HE  abdomen,  or  lower  belly,  extends  froi 


the  lower  extremity  of  the  fternum,  or  tl 
hollow,  ufually  called  the  pit  of  the  ftomacl 
and  more  properly  fcrobiculus  cordis^  to  the  lo^ 
er  part  of  the  trunk. 

It  is  diftinguilhed  into  three  divifions  calle 
regions ; of  thefe  the  upper  one,  which  is  called 
the  epigajlric  region^  begins  immediately  und(‘ 
the  fternum,  and  extends  to  within  two  fingei 
breadth  of  the  navel,  where  the  middle  or  nm 
bilical  region  begins,  and  reaches  to  the  fame  dilf 
lance  below  the  navel.  The  third,  which  i 
called  the  hypogqftric^  includes  the  reft  of  th 
abdomen,  as  far  as  the  os  pubis. 

Each  of  thefe  regions  is  fubdivided  into  thr^ 
others ; two  of  which  compofe  the  fides,  am 
the  other  the  middle  part  of  each  region.  ' 

The  middle  part  of  the  upper  region  is  calle' 
epigajirium^  and  its  two  fides  Th(j 

middle  part  of  the  next  region  is  the  umbilica 
region,  properly  fo  called,  and  its  two  fides  ari  | 
the  flanks,  or  iliac  regions.  Laftly,  the  middli : 
part  of  the  lower  region  retains  the  name  of  hy 
pogaftrium,  and  its  fides  are  called  inguina  oii 
groins.  The  back  part  of  the  abdomen  bearij 
the  name  of  lumbar  region. 


Thdi 


^,?ART  III.  OF  THE  ABDOMEN.  239 

I Thefe  are  tfie  divifions  of  the  lower  belly, 
\Arhich  are  neceflary  to  be  held  in  remembrance, 
as  they  frequently  occur  in  furgical  and  anato- 
mical writing.  We  will  now  proceed  to  exa- 
mine the  contents  of  the  abdomen ; and  after 
1 having  pointed  out  the  names  and  arrangement 
.of  the  feveral  vifcera  contained  in  it,  defcribe 
each  of  them  feparately. 

After  having  removed  the  Ikin,  adipofe  mem- 
brane, and  abdominal  mufcles,  we  difcover  the 
, peritonsEum  or  membrane  that  envelopes  all  the 
rifcera  of  the  lower  belly.  This  being  opened, 
the  firft  part  that  prefents  itfelf  is  the  omentum 
□r  cawl,  floating  on  the  furface  of  the  inteftines, 

1 which  are  likewife  feen  every  where  loofe  and 
moift,  and  making  a great  number  of  circum- 
volutions through  the  whole  cavity  of  the  abdo- 
men. The  ftomach  is  placed  in  the  epigaftrium, 
and  under  the  ftomach  is  the  pancreas.  The 
liver  fills  the  right  hypochondrium,  and  the 
fpleen  is  fituated  in  the  left.  The  kidneys  are 
feen  about  the  middle  of  the  lumbar  region,  and 
the  urinary  bladder  and  parts  of  generation  are 
are  feated  in  the  lower  divifion  of  the  belly. 

Sect.  I.  Of  the  Peritoneum. 

The  peritonsEum  is  a ftrong  fimple  mem- 
brane, by  which  all  the  vifcera  of  the  abdomen 
are  furrounded,  and  in  fome  meafure  fupported. 
Many  anatomical  writers,  particularly  Winflow, 

have 


540  ' OF  THE  ABDOMEN.  Part  HI.  j 

have  defcribed  it  as  being  compofed  of  two  dif- 1 
membranous  laminse  ; but  tbeir  defcripdoq 
feems  to  be  erroneous.  What  perhaps  appeared 
to  be  a fecond  lamina,  being  found  to  be  hmply 
a cellular  coat,  which  fends  off  productions  to 
the  blood-veffels  paffing  out  of  the  abdominal 
cavity.  The  aorta  and  vena  cava  likewife  de- 
rive a covering  from  the  fame  membrane,  which 
feems  to  be  apjrt  of  the  cellular  membrane  we 
-have  already  defcribed. 

The  peritonasum,  by  its  productions  and  re- 
duplications, envelopes  the  greateft  part  of  the 
abdominal  vifcera.  It  is  foft,  and  capable  oI 
confiderable  extenfion  ; and  is  kept  fmooth  and 
moift  by  a vapour,  which  is  conftantly  exhaling ; 
from  its  inner  furface,  and  is  returned  again  intoj 
the  circulation  by  the  abforbents. 

This  moift  ure  not  only  contributes  to  the  foft- 
nefs  of  the  peritonseum,  but  prevents  the  attri- 
tion, and  other  ill  effects  which  would  other- 
wife  probably  be  occafioned,  by  the  motion  of  i 
the  vifcera  upon  each  other. 

When  this  fluid  is  fupplied  in  too  great  a 
quantity,  or  the  abforbents  becorne  incapable  of 
carrying  it  off,  it  accumulates,  and  conftitutes  an|i 
afcites  or  dropfy  of  the  belly  ; and  when  by 
any  means  the  exhalation  is  difcontinued,  the 
peritonasum  thickens,  becomes  difeafed,  andthej 
vifcera  are  fometimes  found  adhering  to  eaelil 
other. 

The  peritonaeum  is  not  a very  vafcular  menvJ 
ft  braneJ 


Part  III.  OF  THF  ABDOMEN.  341 

brane.  In  a found  Hate  it  feems  to  be  endued 
with  little  or  no  feeling,  and  the  nerves  that 
pafs  through  it  appear  to  belong  to  the  abdomi- 
nal mufcles. 

Sect.  II.  Of  the  Omentum* 

The  omentum,  epiploon,  or  cawl,  is  a dou- 
ble membrane,  produced  from  the  peritonseum. 
It  is  interlarded  with  fat,  and  adheres  to  the  fto- 
nach,  fpleen,  duodenum,  and  colon  ; from  thence 
ranging  down  loofe  and  floating  on  the  furface 
rf  the  inteftines.  Its  fize  is  different  in  different 
ubjedls.  In  fome  it  defcends  as  low  as  the  pel- 
/is,  and  it  is  commonly  longer  at  the  left  fide 
han  the  right. 

This  part,  the  fituation  of  which  we  have  juft 
low  defcribed,  was  the  only  one  known  to  the 
ncients  under  the  name  of  epiploon  ; but  at  pre- 
ent  we  diftinguifh  three  omenta,  viz.  omcntuITt 
lagniim  collco  gafricum^  omentum  parvum  hepa-^ 
'CO  gafricum^  and  omentum  coUcum.  Tliey  all 
gree  in  being  formed  of  two  very  delicate  la- 
linse,  feparated  by  a thin  layer  of  cellular  mem- 
' rane. 

The  omentum  magnum  colico  gaftricum,  of 
rhich  we  have  already  fpoken,  derives  its  ar- 
mies from  the  fplenetic  and  hepatic.  Its  veins 
Tminate  in  the  vena  portae.  Its  nen’^es,  which 
•e  very  few,  come  from  the  fplenetic  and  he- 
a.tic  plexus. 

CL 


The 


^42  OF  THE  ABDOMEN.  Part  III. 

The  omentum  parvum  hepatico  gaftricum, 
abounds  lefs  with  fat  than  the  great  epiploon.  It 
begins  at  the  upper  part  of  the  duodenum,  ex- 
tends along  the  lelfer  curvature  of  the  ftomach 
as  far  as  the  oefophagus,  and  terminates  about 
the  neck  of  the  gall-bladder,  and  behind  the 
left  ligament  of  the  liver,  fo  that  it  covers  the 
lefler  lobe ; near  the  beginning  of  which  we  may 
obferve  a fmall  opening,  firft  defcribed  by  Win- 
dow, through  which  the  whole  pouch  may  ea- 
fily  be  diftended  with  air  (x).  The  velfels  of 
the  omentum  parvum  are  derived  chiefly  from 
the  coronary  ftomachic  arteries  and  veins. 

The  omentum  olicum  begins  at  the  fore  part 
of  the  coecum  and  right  fide  of  the  colon.  It  ap- 
pears as  a hollow  conical  appendage  to  thefe 
inteftines,  and  ufually  terminates  at  the  backj 
of  the  omentum  magnum.  It  feems  to  be  no^ 
thing  more  than  a membranous  coat  of  th(|| 
coecum  and  colon,  affuming  a conical  fhape  with' 
air.  I 

The  ufes  of  the  omentum  are  not  yet  fatisfaci 
toril'y  determined.  Perhaps  by  its  foftnefs  anJ 
loofenefs  it  may  ferve  to  prevent  thofe  adhefioni; 
of  the  abdominal  vifcera,  which  have  been  foum 
Co  take  place  when  the  fat  of  the  omentum  ha 
been  much  wafted.  Some  authors  have  fup 

pofe( 

(x)  This  membranous  bag,  though  exceedingly  thin  an 
rranfparent,  is  found  capable  of  fupporting  mercury>  throw 
into  it  by  the  fame  channel. 


Part  III.  OF  THE  ABDOMEN.  .243 

pofed,  that  it  affifts  in  the  preparation  of  bile  j 
but  this  idea  is  founded  merely  on  conjecture. 

Sect.  III.  Of  the  Stomach, 

The  ftomach  is  a membranous  and  mufcular 
bag,  in  fliape  notunlike  a bagpipe,  lying  acrofs 
the  upper  part  of  the  abdomen,  and  inclining  ra- 
ther more  to  the  left  than  the  right  fide. 

It  has  two  orifices,  one  of  which  receives ' the 
end  of  the  oefophagus,  and  is  called  the  cardia^ 
and  fometimes  the  left  and  upper  orifice  of  the 
flomach ; though  its  fituation  is  not  much  higher 
than  the  other,  which  is  ftyled  the  right  and  in- 
ferior orifice,  and  more  commonly  the  pylorus  : 
both  thefe  openings  are  more  elevated  than  the 
body  of  the  ftomach. 

The  aliment  pafTes  down  the  oefophagus  into 
the  flomach  through  the  cardia,  and  after  hav- 
ing undergone  the  neceffary  digeftion,  paffes 
out  at  the  pylorus  where  the  inteflinal  canal 
commences. 

The  flomach  is  compofed  of  four  tunics  or 
coats,  which  are  fo  intimately  connected  toge- 
ther that  it  requires  no  little  dexterity  in  the  ana- 
tomifl  to  demonflrate  them.  The  exterior  one 
is  membranous,  being  derived  from  the  perito- 
nseum. — The  fecond  is  a mufcular  tunic,  com- 
pofed of  flefhy  fibres  which  are  in  the  greatefl 
number  about  the  two  orifices. — The  third  is 
called  the  nervous  coat,  and  within  this  is  the 

villous 


244  OF  THE  ABDOMEN. 

villous  or  velvet-like  coat  which  conlpofes  the 

infide  of  the  ftomach. 

The  two  laft  coats  being  more  extenfive  than 
the  two  firft,  form  the  folds,  which  are  obferv- 
ed  every  where  in  the  cavity  of  this  vifcus,  and 
more  particularly  about  the  pylorus  ; where  they 
feem  to  impede  the  too  hafty  exclulion  of  the 
aliment,  making  a confiderable  plait,  called  val- 
vula  pylori. 

The  inner  coat  is  conftantly  moiftened  by  a 
mucus,  which  approaches  to  the  nature  of  the 
faliva,  and  is  called  the  gaftric  juice  ; this  liquor 
has  been  fuppofed  to  be  fecreted  by  certain  mi- 
nute glands  (y)  feated  in  the  nervous  tunic,  whofe 
excretory  dudfs  open  to  the  furface  of  the  villous 
coat. 

The  arteries  of  the  ftomach  called  the  gaf- 
tric  arteries  are  principally  derived  from  the  cse- 
liac  ; fome  of  its  veins  pafs  to  the  fplentic,  and 
others  to  the  vena  portae  ; and  its  nerves  are 
chiefly  from  the  eight  pair  or  par  vagum. 

The  account  given  of  the  tunics  of  the  fto- 
mach may  be  applied  to  the  whole  alimentary 

canal ; I 


(y)  Heifter,  fpeaking  of  thefe  glands,  very  properly  fays, 
“ in  porch  facile,  in  homine  raro  oblervantur  for  although 
many  anatomical  writers  have  defcribed  their  appearance 
and  figure,  yet  they  do  not  feem  to  have  been  hitherto  fa- 
tisfaftorily  demonflrated  in  the  human  ftomach ; and  the 
gaftric  juice  is  now  more  generally  believed  to  be  derived 
from  the  exhalent  arteries  of  the  ftomach. 


Part  III.  OF  THE  ABDOMEN.  145 

canal  j for  both  the  oefophagus  and  inteftines 
are,  like  this  vifcus,  compofed  of  four  coats. 

Before  we  defcribe  the  courfe  of  the  aliment 
and  the  ufes  of  the  ftomach,  it  will  be  neceffary 
to  fpeak  of  other  parts  which  affift  in  the  pro- 
cefs  of  digeftion. 

Sect.  IV.  Of  the  Oefophagus. 

The  oefophagus  or  gullet  is  a membranous 
and  mufcular  canal,  extending  from  the  bottom 
of  the  mouth  to  the  upper  orifice  of  the  ftomach. 
— Its  upper  part  where  the  aliment  is  received  is 
lhaped  fomewhat  like  a funnel,  and  is  called  the 
pharynx. 

From  hence  it  runs  down  clofe  to  the  bodies 
of  the  vertebrae  as  far  as  the  diaphragm,  in  which 
there  is  an  opening  through  which  it  palfes,  and 
then  terminates  in  the  ftomach  about  the  ele- 
venth or  twelfth  vertebra  of  the  back. 

The  oefophagus  is  plentifully  fupplied  with 
arteries  from  the  external  carotid,  bronchial,  and 
fuperior  intercoftal  arteries ; its  veins  empty 
themfelves  into  the  vena  azygos,  internal  jugu- 
lar, and  mammary  veins,  &c. 

Its  nerves  are  derived  chiefly  from  the  eighth 
pair. 

We  likewife  meet  with  a mucus  in  the  oefopha- 
gus, which  every  where  lubricates  its  inner  furface, 
and  tends  to  affift  in  deglutition. — This  mucus 
feems  to  be  fecreted  by  very  minute  glands,  like 

the 


246 


OF  THE  ABDOMFN.  Part  III. 


the  mucus  in  other  parts  of  the  alimentary  ca- 
nal. 


The  inteftines  form  a canal,  which  is  ufually 
fix  times  longer  than  the  body  to  which  it  be- 
longs. This  canal  extends  from  the  pylorus,  or 
inferior  orilice  of  the  ftomach,  to  the  anus. 

It  will  be  eafily  underftood,  that  a part  of  fuch 
great  length  muft  neceffarily  make  many  circum- 
volutions, to  be  confined  with  fo  many  other 
vifcera  wiTdn  the  cavity  of  the  lower  belly. 

Although  the  inteftines  are  in  facft,  as  we  have 
obferved,  only  one  long  and  extenfive  canal,  yet 
different  parts  have  been  diftinguilhed  by  dijfFe- 
rent  names. 

The  inteftines  are  firft  diftinguifhed  into  two 
parts,  one  of  which  begins  at  the  ftomach,  and 
is  called  the  thin  or  fmall  intejlines^  from  the 
fmall  fize  of  the  canal,  when  compared  with  the 
other  part,  which  is  called  the  large  intejiines^ 
and  includes  the  lower  portion  of  the  canal  down 
to  the  anus. 

Each  of  thefe  parts  has  it  its  fubdivifions. — 
The  fmall  inteftines  being  diftinguifhed  into 
duodenum,  jejunum,  and  ilium,  and  the 
larger  portion  into  coecum,  colon,  and  rec- 
tum. 

The  fmall  inteftines  fill  the  middle  and  fore 
parts  of  the  belly,  while  the  large  inteftine 


Sect.  V.  Of  the  Intefines. 


Part  III.  OF  THE  ABDOMEN.  247 

the  fides  and  both  the  upper  and  lower  parts  of 
the  cavity. 

The  duodenum,  which  is  the  firft  of  the 
fmall  inteftines,  is  fo  called,  becaufe  it  is  about 
1 2 inches  long.  It  begins  at  the  pylorus  and 
terminates  in  the  jejunum,  which  is  a part  of 
the  canal  obferved  to  be  ufually  more  empty  than 
the  other  inteftines. — This  appearance  gives  it 
its  name,  and  likewife  ferves  to  point  out  where 
it  begins. 

The  next  divifion  is  the  ilium,  which  of  it- 
felf  exceeds  the  united  length  of  the  duodenum 
and  jejunum,  and  has  received  its  name  from  its 
numerous  circumvolutions.  The  large  circum- 
volution of  the  ilium  covers  the  firft  of  the  large 
inteftines  called  the  cacum  (x)  which  feems  pro- 
perly to  belong  to  the  colon,  being  a kind  of 
pouch  of  about  four  fingers  in  width,  and  near- 
ly of  the  fame  length,  having  anteriorly  a lit- 
tle appendix,  called  appendix  cceci. 

The  coecum  is  placed  in  the  cavity  of  the  os 
ilium  on  the  right  fide,  and  terminates  in  the 
colon,  which  is  the  largeft  of  all  the  inteftines. 

This  inteftine  afcends  by  the  right  kidney  to 
which  it  is  attached,  paifes  under  the  hollow 

part 

/ 

(x)  Anatomlfts  have  differed  with  refpect  to  this  divifion 
of  the  inteftines. — The  method  here  followed  is  now  gene- 
rally adopted ; but  there  are  authors  who  allow  the  name 
of  cacim  only,  to  the  little  appendix,  which  has  likewife 
been  called  the  vermiform  appendix^  from  its  rei'emblance  to 
a v/orm  in  fize  and  length. 


OF  THE  ABDOMEN.  Part  III. 
part  of  the  liver,  and  the  bottom  of  the  ftomach, 
to  the  fpleen,  to  which  it  is  likewife  fecured,  as 
it  is  alfo  to  the  left  kidney ; and  from  thence 
pafles  down  towards  the  os  facrum,  where,  from 
its  ftraight  courfe,  the  canal  begins  to  take  the 
name  of  reBum. 

There  are  three  ligamentous  bands  extending 
through  the  whole  length  of  the  colon,  which, 
by  being  fhorter  than  its  two  inner  coats,  ferve 
to  increafe  the  plaits  on  the  inner  furface  of  this 

gut. 

The  anus  which  terminates  the  inteftinum 
redum,  is  furnifhed  with  three  mufcles  ; one  of 
thefe  is  compofed  of  circular  fibres,  and  from  its 
life  in  {hutting  the  paifage  of  the  anus  is  called 
fphiiiBer  ani. 

The  other  two  are  the  levatores  ani^  fo  called, 
becaufe  they  elevate  the  anus  after  dejedion. 
When  thefe  by  palfy,  or  any  other  difeafe,  lofe 
the  power  of  contrading,  the  anus  prolapfes  ; 
and  whenthefphinderis  affeded  byfimilar  caufes, 
the  feces  are  voided  involuntarily. 

It  has  been  already  obferved,  that  the  inteftinal 
canal  is  compofed  of  four  tunics  ; but  it  remains ' 
to  be  remarked,  that  here,  as  in  the  ftomach, 
the  two  inner  tunics  being  more  extenfive  than 
the  other  two,  form  the  plaits  which  are  to  be 
feen  in  the  inner  furface  of  the  inteftines,  and 
are  called  valvula  conniventes. 

Some  authors  have  confidered  thefe  plaits  as 
tending  to  retard  the  motion  of  the  feces,  in 

order 


Part  III.  OF  THE  ABDOMEN,  249 

order  to  afford  more  time  for  the  feparation  of  the 
chyle ; but  there  are  others  who  attiibute  to  them 
a different  ufe  : they  contend,  that  thefe  valves, 
by  being  naturally  inclined  downwards,  can- 
not impede  the  defcent  of  the  fseces,  but  that 
they  are  intended  to  prevent  their  return  up- 
wards. 

They  are  probably  deftined  for  both  thefe  ufes; 
for  although  thefe  folds  incline  to  their  lower 
fide,  yet  the  inequalities  they  occafion  in  the  ca- 
nal are  fufficient  to  retard,  in  fome  meafure,  the 
progreffive  motion  of  the  fseces,  and  to  afford  a 
greater  fiirface  of  the  absorption  of  chyle,  and 
their  natural  pofition  feems  to  oppofe  Itielf  to  the 
return  of  the  aliment. 

Befides  thefe  valvules  conniventes^  there  is  one 
more  confiderable  than  the  reft,  called  the  valve 
of  the  colon  ; which  is  found  at  that  part  of  the 
canal  where  the  inteftinum  ilium  is  joined  to 
the  colon.  'This  valve  permits  the  alimentary 
pulp  to  pafs  downwards,  but  Serves  to  prevent 
its  return  upwards  ; and  it  is  by  this  valve,  that 
glyfters  are  prevented  from  paffing  into  the  fmall 
inteftines  (y). 

Of  the  little  vermiform  appendix  of  the  coe- 
cum,  it  v/ill  be  fufHcient  to  fay,  that  its  ufes  have 

never 

(y)  This  is  not  invariably  the  cafe,  for  the  contents  of  a 
glyfter  have  been  found  not  only  to  reach  the  fcnall  intef- 
tines, but  to  be  voided  at  the  mouth.  Such  infiances,  how- 
ever, are  not  common. 


■■m 

2JO  OF  THE  ABDOMEN.  Part  111.^ 

never  yet  been  afcertained.-  In  birds  we  meet 
with  two  of  thefc  appendices. 

The  inteftines  are  lubricated  by  a conftant 
fupply  of  mucus,  which  is  probably  fecreted  by 
very  minute  folicies  (z).  This  mucus  promotes 
the  defcent  of  the  alimentary  pulp,  and  in  fome 
meafure  defends  the  inner  furface  of  the  intef-  , 
tines  from  the  irritation  to  which  it  would,  per- 
haps, otherwife  be  continually  expofed  from  the 
aliment ; and  which,  when  in  a certain  degree, . 
excites  a painful  diforder  called  co/ic,  a name 
given  to  the  difeafe,  becaufe  its  moft  ufual  feat 
is  in  the  inteftinum  colon. 

The  inteftines  are  likewife  frequently  diftend- 
ed  with  air,  and  this  diftenfion  fometimes  occa- 
fions  pain,  and  conftitutes  the  flatulent  colic. 

The  arteries  of  the  inteftines  are  continuati- 
ons of  the  mefenteric  arteries,  which  are  deriv- 
ed in  two  confiderable  branches  from  the  aorta. 
— The  redundant  blood  is  carried  back  into  the 
vena  portarum. 

In 

(z)  Some  writers  have  diftingiiinied  thefe  glands  into  mi- 
liary, lenticular,  See. — Brunner  and  Peyer  were  the  firfl  ana- 
tomifts  who  deferibed  the  glands  of  the  inteftines,  and  their 
deferiptions  were  chiefly  taken  from  animals,  thefe  glandular 
appearances  not  feeming  to  have  been  hitherto  fatisfadlorily 
pointed  out  in  the  human  ftibjeft. — It  is  now  pretty  general- 
ly believed,  that  the  mucus  which  every  where  lubricates 
the  alimentary  canal,  is  exhaled  from  the  minute  ends  of  ar- 
teries, and  that  theie  extremities  firft  open  into  a hollow  ve- 
ficle,  from  whence  the  depofited  juice  of  feveral  branches 
flows  out  through  one  common  orifice. 


'art  III.  OF  THE  ABDOMEN.  251 

In  the  refcum  the  veins  are  called  hemorrhoi- 
'al^  and  are  there  diftinguifned  into  internal  and 
xternal ; the  rirft  are  branches  of  the  inferior 
iiefenteric  vein,  but  the  latter  pafs  into  other 
'eins.  Sometimes  thefe  veins  are  diftended  with 
)lood  from  obftrudtions,  from  weaknefs  of  their 
:oats,  or  from  other  caufes,  and  what  we  call 
he  ha??io?Thoids  takes  place.  In  this  difeafe  they 
ire  fometimes  ruptured  ; and  the  difcharge  of 
)lood  which  confequently  follovrs,  has  probably 
)ccafioned  them  to  be  called  hcemorrhoidal  veins. 

The  nerves  of  the  inteftines  are  derived  from 
he  eight  pair. 

Sect.  VI.  Of  the  Mefentery. 

The  name  of  the  mefentery  implies  the  litua- 
tion  amidft  the  inteftines.  It  is  in  hidt  a part  of 
the  peritonseum,  being  a reduplication  (a)  of  that 

membrane 

(a)  He  who  only  reads  of  the  reduplication  of  mem- 
branes, will  perhaps  not  ealily  underftand  how  the  peritc- 
nseura  and  pleura  are  rellecled  over  the  vifcera  in  their  feveral 
cavities  ; for  one  of  thefe  ferves  the  fame  purpofes  in  the  tho- 
rax that  the  other  does  in  the  abdomen.  This  dilpofition, 
for  the  difcovery  of  which  we  are  indebted  to  modem  anato- 
mies, conftitutes  a curious  part  of  anatomical  knowledge; 
but  the  ftudenp  unaided  by  experience,  and  alTifled  only  by 
what  the  limits  of  this  work  would  permit  us  to  fay  on  the 
occafion,  would  probably  imbibe  only  confufed  ideas  of  the 
matter ; and  it  will  perfedlly  anfwer  the  prefent  purpofe,  if 
he  confiders  the  mefentery  as  a membiane  attached  by  one 
of  its  fides  to  the  lumbar  vertebra,  and  by  the  other  to  the 
iatellines. 


252  OF  THE  ABDOMEN.  Part  Il| 

membrane  from  each  fide  of  the  lumbar  verte 
brae,  to  which  it  is  firmly  attached,  fo  that  it  ii 
formed  of  two  laminae,  connected  to  ea^ch  othe 
by  cellular  membrane. 

The  inteftines,  in  their  different  circumvolu 
tions,  form  a great  number  of  arches,  and  th 
mefentry  accompanies  them  through  all  thef 
turns  ; but  by  being  attached  only  to  the  holloM, 
part  of  each  arch ; it  is  found  to  have  only  , 
third  of  the  extent  of  the  inteftines. 

That  part  of  this  membrane  which  accompa 
nies  the  fmall  inteftines  is  the  mefentery^  properl] 
fo  called  ; but  thofe  parts  of  it  which  are  attach 
ed  to  the  colon  and  redtum  are  diftinguiflied  b] 
the  names  of  mefo-colon  and  mefo~reBum. 

There  are  many  conglobate  glands  difperfec 
through  this  double  membrane,  through  whicl 
the  ladfeals  and  lymphatics  pafs  in  their  way  tc 
the  thoracic  dud;.  The  blood-veflels  of  the 
mefentery  were  defcribed  in  fpeaking  of  the  in*| 
teftines.  I 

This  membrane,  by  its  attachment  to  the 
vertebrse,  ferves  to  keep  the  inteftines  in  their  na- 
tural fituation.  The  idea  ufually  formed  of  the^ 
colic  called  mijerere^  is  perfedly  erroneous ; itj 
being  impoflible  that  the  inteftines  can  be  twifted, 
as  many  fuppofe  they  are,  in  that  difeafe,  their 
attachment  to  the  mefentery  effedually  prevent- 
ing fuch  an  accident ^but  a difarrangement 

fometimes  takes  place  in  the  inteftinal  canal  it- 
fclf,  which  is  productive  of  difagreeable  and 

fome- 


krt  hi.  of  thl  abdomen.  253 

MTietimes  fatal  confequences.- — This  is  by  an  in- 
•ofufception  of  the  inteftine,  an  idea  of  which 
lay  be  eafily  formed,  by  taking  the  finger  of 
glove,  and  involving  one  part  of  it  within  the 
■her. 

If  inflammation  takes  place,  the  ftrifture  In 
lis  cafe  is  increafed,  and  the  periftaltic  motion 
f the  inteftines  (by  which  is  meant  the  pro- 
reflive  motion  of  the  fseces  downwards)  is  in- 
erted, and  what  is  called  the  iliac  pajfion  takes 
lace.  The  fame  effedt  may  be  occafioned  by 
defcent  of  the  inteftine,  or  of  the  omentum 
ither  with  it  or  by  itfelf,  and  thus  conftituting 
(That  is  called  an  hernia  or  rupture ; a term  by 
v^hich  in  general  is  meant  the  falling  down  or 
)rotrufion  of  any  part  of  the  inteftine  or  omen- 
urn,  which  ought  naturally  to  be  contained  with- 
n the  cavity  of  the  belly. 

To  convey  an  idea  of  the  manner  in  which 
iich  a defcent  takes  place,  it  will  be  neceflary  to 
)bferve,  that  the  lower  edge  of  the  tendon  of 
T the  mufculus  obliquus  externus,  is  ftretched 
From  the  fore-part  of  the  os  ilium  or  haunch- 
Done  of  the  os  pubis,  and  conftitutes  what  is 
called  Pouparfs  or  Fallopius's  ligament^  forming 
an  opening,  through  which  pafs  the  great  crural 
artery  and  vein.  Near  the  os  pubis  the  fame 
tendinous  fibres  are  feparated  from  each  other^ 
and  form  an  opening  on  each  fide,  called  the 
abdominal  ring,  through  which  the  fpermatic 
veflels  pafs  in  men,  and  the  ligamenta  uteri  in 

women. 


254 

women. 


OF  THE  ABDOMEN.  Part  111 


I n confeqoence 


of  violent  efibits,  o; 


perhaps  of  natural  caufes,  the  inteftines  are  foun(! 
Ibmetirnes  to  pafs  through  thefe  openings  ; bui 
the  peritonaeum  v/hich  indofes  them  when  ir 
their  natural  cavity,  ftiil  continues  to  furrounc 
them  even  in  their  natural  cavity,  ftiil  continues 
to  furround  them  even  in  their  defcent.  This 
membrane  does  not  become  torn  or  lacerated  by 
the  violence,  as  might  be  eafily  imagined  ; but 
its  dilatibility  enables  it  to  pafs  out  with  the  vif- 
cus,  which  it  indofes  as  it  were  in  a bag,  and 
thus  forms  wdiat  is  called  the  hernial fac. 

If  the  hernia  be  under  Poupart’s  ligamenfj^ 
it  is  calledy^7?/ora/ ; if  in  the  ^rdn\  inguinal  (b), 
and  fcrotal^  if  in  the  fcrotum.  Different  names 
are  likewife  given  to  the  hernia  as  the  contents^ 
of  the  fac  differ,  whether  of  omentum  only  or 
inteftine,  or  both  ; — but  thefe  definitions  more 
properly  belong  to  the  province  of  furgery. 


Sect.  VII  Of  the  Pancreas. 


The  pancreas  is  a conglomerate  gland  placed 
behind  the  bottom  of  the  ftomach,  towards  the 
firft  vertebra  of  the  loins  5 fhaped  like  a dog’s 
tongue  with  its  point  ftretched  out  towards  the 
fpleen,  and  its  other  end  extending  towards  the 
duodenum.  It  is  about  eight  fingers  breadth  in 

length, 


(b)  The  hernia  congenita  will  be  confidered  with  themiile 
organs  of  generation,  with  which  it  is  intimately  connefted. 


Part  III.  OF  THE  ABDOMEN.  255 
length,  two  or  three  in  width,  and  one  in  thick- 
nefs. 

This  vifcus,  which  is  of  a y ellowifh  colour, 
fomewhat  inclined  to  red,  is  covered  with  a mem- 
brane which  it  derives  from  the  peritonaeum. 
Its  arteries,  which  are  rather  numerous  than 
large,  are  derived  chiefly  from  the  fplenic  and 
hepatic,  and  its  veins  pafs  into  the  veins  of  the 
fame  name. — Its  nerves  are  derived  from  the  in- 
tercoftal. 

The  many  little  glands  of  which  it  has  been 
obferved  the  pancreas  is  compofed,  all  ferve  to 
fecrete  a liquor  called  the  pancreatic  juice^  which 
in  its  colour,  confiftence,  and  other  properties, 
does  not  feem  to  differ  from  the  faliva.  Each  of 
thefe  glands  fends  out  a little  excretory  du£t, 
which,  uniting  with  others,  help  to  form  larger 
dudfs  ; and  all  thefe  at  laft  terminate  in  one  com- 
mon excretory  du£t  (firft  difcovered  by  Virtfun- 
gus  in  1642),  which  runs  through  the  middle 
of  the  gland,  and  is  now  ufually  called  diiBus 
pancreaticus  Virtfimgi.  This  canal  opens  into  the 
inteftinum  duodenum,  fometimes  by  the  fame 
orifice  with  the  biliary  dud:,  and  fometimes  by 
a diftind  opening.  The  liquor  it  difcharges  be- 
ing of  a mild  and  infipid  nature,  ferves  to  dilute 
the  alimentary  pulp,  and  to  incorporate  it  more 
eafily  with  the  bile. 


Sect. 


256 


OF  THE  ABDOMEN.  Part  III. 
Sect.  VIII.  Of  the  Liver, 

The  liver  is  avifcusof  confiderable  fize,  and 
of  a reddifh  colour  ; convex  fuperiorly  and  an- 
teriorly where  it  is  placed  under  the  ribs  and  di- 
aphragm, and  of  an  unequal  furface  pofteriorly. 
It  is  chiefly  fituated  in  the  right  hypochondrium, 
and  under  the  falfe  ribs  ; but  it  like  wife  extends 
into  the  epigaftric  region,  where  it  borders  upon 
the  fliomach.  It  is  covered  by  a production  of 
the  peritonaeum,  which  ferves  to  attach  it  by 
three  of  its  reduplications  to  the  falfe  ribs.  Theie 
reduplications  are  called  ligaments^  though  very 
different  in  their  texture  from  what  are  called  by 
the  fame  name  in  other  parts  of  the  body.  The 
umbilical  cord,  too,  which  in  the  foetus  is  per- 
vious, gradually  becomes  a fimple  ligament  after 
birth  ; and,  by  pafling  to  the  liver,  ferves  like- 
wife  to  fecure  it  in  its  fituation. 

At  the  pofterior  part  of  this  organ  where  the 
umbilical  veffels  enter,  it  is  found  divided  into 
two  lobes.  Of  thefe,  the  largeft  is  placed  in  the 
right  hypochondrium  ; the  other,  which  covers 
part  of  the  flomach,  is  called  the  little  lobe.  All 
the  t'effels  which  go  to  the  liver  pafs  in  at  the 
fiffure  we  have  mentioned  ; and  the  production 
of  the  peritonaeum,  which  invefts  the  liver,  was 
defcnbed  by  Gliflbn,  an  Englifh  anatomifl,  as 
accompanying  them  in  their  paffage,  and  fur- 
rounding  them  like  a glove  ; hence  this  produc- 
2 tion 


Part  III.  OF  THE  ABDOMEN.  257 
tion  has  been  commonly  known  by  the  name  of 
capfula  of  Glijfon  : but  it  appears  to  be  chiefly  a 
continuation  of  the  cellular  membrane  which  co- 
vers the  vena  porta  ventralis. 

The  liver  was  confidered  by  the  ancients  as 
an  organ  deftined  to  prepare  and  perfect  the 
blood  ; but  later  difcoveries  have  proved,  that 
this  opinion  was  wrong,  and  that  the  liver  is  a 
glandular  fubftance  formed  for  the  fecretion  of 
the  bile. 

The  blood  is  conveyed  to  the  liver  by  the  he- 
patic artery  and  the  vena  porta.  This  is  contra- 
ry to  the  mode  of  circulation  in  other  parts, 
where  veins  only  ferve  to  carry  off  the  redundant 
blood : but  in  this  vifcus  the  hepatic  artery, 
which  is  derived  from  the  caeliac,  is  principally 
deftined  for  its  nourifhment ; and  the  vena  por- 
ta, which  is  formed  by  the  union  of  the  veins 
from  moft  of  the  abdominal  vifcera,  furnifties  the 
blood  from  which  the  bile  is  chiefly  to  be  feparat- 
ed  ; fo  that  thefe  two  feries  of  veflels  ferve  very 
diftindt  purpofes.  The  vena  porta,  as  it  is  rami- 
fied through  the  liver,  performs  the  office  both 
of  a vein  and  an  artery ; for  like  the  former  it 
returns  the  blood  from  the  extremities  of  arte- 
ries, while  as  the  latter  it  prepares  it  for  fecrc- 
tion. 

The  nerves  of  the  liver  are  branches  of  the 
intercoftal  and  par  vagum.  The  bile,  after  be- 
ing feparated  from  the  mafs  of  blood,  in  a man- 
ner of  which  mention  will  be  made  in  another 

R place 


258  OF  THE  ABDOMEN.  Part  III, 
place,  is  conveyed  out  of  this  organ  by  very  mi- 
nute excretory  du£ts,  called  poribiliarii ; thefe 
uniting  together  like  the  excretory  du£ts  in  the 
pencreas,  gradually  form  larger  ones,  which  at 
length  terminate  in  a confiderable  canal  called 
iluStus  hepaticus. 

Sect.  IX.  Of  the  Gall-bladder. 

The  gall-bladder  is  a little  membranous  bag, 
fliapcd  like  a pear,  and  attached  to  the  pofterior 
and  almoft  inferior  part  of  the  great  lobe  of  the 
liver. 

It  has  two  tunics  ; of  which  the  exterior  one 
is  a production  of  the  peritonaeum.  The  inte- 
rior^ or  villous  coat,  is  fupplied  with  a mucus 
that  defends  it  from  the  acrimony  of  the  bile. 
Thefe  two  coverings  are  intimately  connected  by 
means  of  cellular  membrane,  which  from  its  firm 
gliftening  appearance  has  generally  been  fpoken 
of  as  a mufcular  tunic. 

The  gall-bladder  is  fupplied  with  blood-veifeh 
from  the  hepatic  arteries.  Thefe  branches  are 
called  the  cyfic  arteries and  the  cyftic  veins  car- 
ry back  the  blood. 

Its  nerves  are  derived  from  the  fame  origin  ai 
thofe  of  the  liver. 

The  neck  of  the  gall-bladder  is  continued  in 
the  form  of  a canal  called  dublus  cyficus,  which 
foon  unites  with  the  duftus  hepaticus  we  deferib- 
ed  as  the  excretory  dud;  of  the  liver  j and  form- 
ing 


Part  III.  OF  THE  ABDOMEN.  255 
ing  one  common  canal,  takes  the  name  of  dulJhis 
choledochus  commimis^  through  which  both  the 
cyftic  and  hepatic  bile  are  difcharged  into  the  du- 
odenum. This  canal  opens  into  the  inteftine  in 
an  oblique  diredion,  firft  paffing  through  the 
exterior  tunic,  and  then  piercing  the  other  coats 
after  running  between  each  of  them  a very  little 
way.  This  oeconomy  ferves  two  ufeful  pur- 
pofes  ; — to  promote  the  difcharge  of  bile  and  to 
prevent  its  return. 

The  bile  may  be  defined  to  be  a natural  liquid 
foap,  fomewhat  unduous  and  bitter,  and  of  a 
yellowifli  colour,  which  eafily  mixes  with  water, 
oil,  and  vinous  fpirits,  and  is  capable  of  diffolv- 
ing  refinous  fubftances.  From  fome  late  experi- 
ments made  by  M.  Cadet*,  it  appears  .to  be 
formed  of  an  animal  oil,  combined  with  the  al-» 
kaline  bafe  of  fea-falt,  a fait  of  the  nature  of 
milk,  and  a calcareous  earth  which  is  (lightly  fer- 
ruginous. 

Its  definition  feems  fufficiently  to  point  out 
the  ufes  for  which  it  is  intended  (c).  It  blends 
the  alimentary  mafs,  by  dividing  and  attenuating 
it ; corredfs  the  too  great  difpofition  to  aeefcency, 
which  the  aliment  acquires  in  the  ftomach  ; and, 
finally,  by  its  acrimony,  tends  to  excite  the  pe- 
riftaltic  motion  of  the  inteftines. 

R a After 

* Mem.  de  f AcacL  lies  Sciences.  1767. 

(c)  The  ancients,  who  were  not  acquainted  with  the  real 
ule  of  the  liver,  confidered  the  bile  as  an  eKcreinentitious 
and  ufelefs  fluid. 


i6o  GF  THE  ABDOMEN.  Part  III. 

After  what  has  been  faid,  it  will  be  conceived 
that  there  are  two  forts  of  bile  ; one  of  which 
is  derived  immediately  from  the  liver  through  the 
hepatic  du£t,  and  the  other  from  the  gall-blad-r- 
der.  Thefe  two  biles,  however,  do  not  effenti- 
ally  differ  from  each  other.  The  hepatic  bile  in- 
deed is  milder,  and  more  liquid  than  the  cyftic, 
which  is  conftantly  thicker  and  yellower ; and 
by  being  bitterer,  feems  to  poffefs  greater  activity 
than  the  other. 

Every  body  knows  the  fonrce  of  the  hepatic 
bile,  that  it  is  fecreted  from  the  mafs  of  blood 
by  the  liver  ; but  the  origin  of  the  cyllic  bile  has 
occafioned  no  little  controverfy  amonjgft  anato- 
mical writers.  There  are  fome  who  contend, 
that  it  is  feparated  in  the  fubftance  of  the  liver, 
from  whence  it  paffes  into  the  gall-bladder 
through  particular  veffels.  In  deer,  and  in  fome 
other  quadrupeds,  as  well  as  in  feveral  birds  and 
fifhes,  there  is  an  evident  communication,  hy 
means  of  particular  veffels,  between  the  liver 
and  the  gall-bladder,  Bianchi,  Winflow,  and 
others,  have  afferted  the  exiftence  of  fuch  veffels 
in  the  human  fubjed:,  and  named  them  hepati- 
cvftic  duSh ; but  it  is.  certain  that  no  fuch  duds 
exift. — ^In  obftrudions  of  the  cyftic  dud,  the 
gall-bladder  has  been  found  fhrivelled  and  emp^ 
ty  : fo  that  we  may  confider  the  gall-bladder  as 
a refervoir  of  hepatic  bile  ; and  that  it  is  an  ef- 
tablifhed  fad,  that  the  whole  of  the  bile  con- 
tained in  the  gall-bladder  is  derived  from  the  li- 
ver > 


Part  III.  OF  THE  ABDOMEN.  261 
ver ; that  it  paflhs  from  the  hepatic  to  the  cyftic 
duft,  aiid  from  that  to  the  gall-bladder.  The 
difference  in  the  colour,  confiftence,  and  tafle  of 
the  bile,  is  merely  the  confequence  of  ftagnation 
and  abforption.  When  the  ftomach  is  diftend- 
od  with  aliment,  this  refervoir  undergoes  a cer- 
tain degree  of  compreffion,  and  the  bile  paffes 
out  into  the  inteftinal  canal ; and  in  the  efforts  to 
vomit,  the  gall-bladder  feeitis  to  be  conftantly  af- 
fedled,  and  at  fuch  times  difcharges  itfelf  of  its 
contents. 

Sometimes  the  bile  concretes  in  the  gall-blad- 
der, fo  as  to  form  what  are  cdX\&di  gall-Jlones  (d). 
When  thefe  concretions  pafs  into  the  cyflic  dud:, 
they  fometimes  occafion  exquifite  pain,  by  dif- 
tending  the  canal  in  their  Way  to  the  duodenum ; 
and  by  lodging  in  the  dudus  choledochus  com- 
munis, and  obflruding  the  courfe  of  the  bile, 
this  fluid  will  be  abforbed,  and  by  being  carried 
back  into  the  circulation  occafion  a temporary 
jaundice. 

Sect.  X.  Of  the  Spleen. 

The  fpleen  is  a foft  and  fpongy  vifcus,  of  a 

bluifh 

(d)  Thefe  concretions  fotnetlines  remain  in  the  gall-blad- 
■der  without  cauling  any  uneafinefs.  Dr.  Heberden  relates, 
that  a gall-ftone  weighing  two  drams  was  found  in  the  gall- 
bladder of  the  late  Lord  Bath,  though  he  had  never  com- 
plained of  the  jaundice,  nor  of  any  di'lbrder  which  he  could 
attribute  to  thatcaufe.  Med.  Tranf.  Vol.  ii. 


262  OF  THE  ABDOMEN.  Part  III. 
bluifh  colour,  and  about  five  or  fix  fingers 
breadth  in  length,  and  three  in  width,  fitu- 
ated  in  the  left  hypochondrium,  between  the 
llomach  and  the  falfe  ribs.  That  fide  of  it  which 
is  placed  on  the  fide  of  the  ribs  is  convex  ; and 
the  other,  which  is  turned  toward  the  ftomach, 
is  concave. 

The  fplenic  artery,  which  is  a branch  from 
the  cseliac,  fupplies  this  vifcus  with  blood,  and 
a vein  of  the  lame  name  carries  it  back  into  the  L 
vena  porta. 

Its  nerves  are  derived  from  a particular  plexusw 
called  the  fpknic^  which  is  formed  by  branches  a 
of  the  intercoftal  nerve,  and  by  the  eight  pair,  | 
or  par  vagum. 

The  ancients,  who  fuppofed  two  forts  of  hile, 
confidered  the  fpleen  as  the  receptacle  of  what 
they  called  atra  bills.  Havers,  who  wrote  pro- 
felfedly  on  the  bones,  determined  its  ufe  to  be 
that  of  fecreting  the  fynovia  ; and  the  late  Mr. 
Hewfon  imagined,  that  it  concurred  with  the 
thymus  and  lymphatic  glands  of  the  body  in 
forming  the  red  globules  of  the  blood.  All  thefe 
opinions  feem  to  be  equally  fanciful.  The  want 
of  an  excretory  druT  has  occafioned  the  real  ufe 
of  this  vifcus  to  be  ftill  doubtful.  Perhaps  the 
blood  undergoes  fome  change  in  it,  which  may 
alfift  in  the  preparation  of  the  bile.  This  is  the 

opinion  of  the  generality  of  modern  phyfiolo- 
gifts  ; and  the  great  quantity  of  blood  with 
which  it  is  fupplied,  together  with  the  courfe  of 

its 


Part  III.  OF  THE  ABDOMEN.  263 
its  veins  into  the  vena  portae,  feem  to  render  this 
notion  probable. 

Sect.  XL  OJ'  the  Glandule  RenaleSy  Kidneys y 
and  Uretas, 

The  glandulse  renales,  which  were  by  the  ’ 
ancients  fuppofed  to  fecrete  the  atra  bilis,  and  by 
them  named  capfula  atrabilares ^ are  two  fiat  bo- 
dies of  an  irregular  figure,  one  on  each  fide  be- 
tween the  kidney  and  the  aorta. 

In  the  foetus  they  are  as  large  as  the  kidneys  : 
but  they  do  not  increafe  afterwards  in  proportion 
to  thofe  parts ; and  in  adults  and  old  people  they 
are  generally  found  fhrivelled,  and  much  wafted. 
They  have  their  arteries  and  veins.  Their  ar- 
teries ufually  arife  from  the  Jplenic  or  the  emul- 
gent,  and  fometimes  from  the  aorta ; and  their 
veins  go  to  the  neighbouring  veins,  or  to  the 
vena  cava.  Their  nerves  are  branches  of  the 
intercoftal. 

The  ufe  of  thefe  parts  is  not  yet  perfedHy 
known.  In  the  foetus  the  fecretion  of  urine  muft 
be  in  a very  fmall  quantity,  and  a part  of  the 
blood  may  perhaps  then  pafs  through  thefe  chan- 
nels, which  in  the  adult  is  carried  to  the  kidneys 
to  fupply  the  matter  of  urine. 

The  kidneys  are  two  in  number,  fituated  one 
on  the  right  and  the  other  on  the  left  fide  in  the 
lumbar  region,  between  the  laft  falfe  rib  and  the 
os  ilium,  by  the  fides  of  the  vertebra.  Each 


■264  OE  THE  ABDOMEN.  Part  III. 
kidney  in  its  figure  refembles  a fort  of  bean, 
which  from  its  fhape  is  called  kidney-bean.  The 
concave  part  of  each  kidney  is  turned  towards 
the  aorta  and  vena  cava  afcendens.  They  are 
furrounded  by  a good  deal  of  fat,  and  receive 
a coat  from  the  peritonaeum  ; and  when  this  is 
removed,  a very  fine  membrane  is  found  inveft- 
ing  their  fubftance  and  the  veffels  which  ramify 
through  them. 

Each  kidney  has  a confiderable  artery  and 
vein,  which  are  called  the  emidgent.  The  arte- 
ry is  a branch  from  the  aorta,  and  the  vein  pafles 
into  the  vena  cava.  Their  nerves,  which  every 
where  accompany  the  blood-veflels,  arife  from  a 
confiderable  plexus,  which  is  derived  from  the 
interpoftal. 

In  each  kidney,  which  in  the  adult  is  of  a 
pretty  firm  texture,  there  are  three  fubftances  to 
be  diftinguiflied  (e).  The  outer  part  is  glandu- 
lar or  cortical,  beyond  this  is  the  vafcular  or  tU'r 
bular  fubftance,  and  the  inner  part  is  papillary  or 
membranous. 

It  is  in  the  cortical  part  of  the  kidney  that  the 
fecretion  is  carried  on  ; the  urine  being  here  re- 
ceived from  the  minute  extremities  of  the  capilla- 
ry arteries,  is  conveyed  out  of  this  cortical  fub-: 
ftance  by  an  infinite  number  of  very  fmall  cylin- 
drical canals  or  excretory  veflels,  which  confti- 

tute 

(e)  The  kidneys  in  the  foetus  are  diflinftly  lobulated ; but 
m the  adult  they  become  perfe<^ly  firm,  fmooth,  and  re- 
gular. 


Part  III.  OF  THE  ABDOMEN.  265 
tute  the  tubular  part.  Thefe  tubes,  as  they  ap- 
proach the  inner  fubftance  of  the  kidney,  gradu- 
ally unite  together  ; and  thus  forming  larger  ca- 
nals, at  length  terminate  in  ten  or  twelve  little 
protuberances  called  papilla^  the  orifices  of  which 
may  be  feen  without  the  affiftance  of  gialfes. 
Thefe  papillae  open  into  a fmall  cavity  or  refer- 
voir  called  the  pelvis  of  the  kidney^  and  formed 
by  a diftimff  membranous  bag  which  embraces 
the  papillae.  From  this  pelvis  the  urine  is  con- 
veyed through  a membranous  canal  which  paifes 
out  from  the  hollow  fide  of  the  kidney,  a little 
below  the  blood  veffels,  and  is  called  ureter. 

The  ureters  are  each  about  as  large  as  a com- 
mon writing-pen.  They  are  fomewhat  curved 
in  their  courfe  from  the  kidneys,  like  the  letter 
f and  at  length  terminate  in  the  pofterior  and 
almoft  inferior  part  of  the  bladder,  at  fome  dif- 
tance  from  each  other.  They  pafs  into  the  blad- 
der in  the  fame  manner  as  the  du<Tus  choledoc- 
dus  communis  pafles  into  the  inteftinum  duode- 
num, not  by  a dired;  paffage,  but  by  an  obliqu6 
courfe  between  the  tv/o  coats  ; fo  that  the  dif- 
charge  of  urine  into  the  bladder  is  promoted, 
whilft  its  return  is  prevented.  Nor  does  this 
mode  of  ftrudure  prevent  the  palTage  of  fluids 
only  from  the  bladder  into  the  ureters,  but  like- 
wife  air  : — for  air  thrown  into  the  bladder  in- 
flates it,  and  it  continues  to  be  diftended  if  a 
Figature  is  pafled  round  its  neck  ; which  feems 

to 


266  OF  THE  ABDOMEN.  Part  lit. 
to  prove  fufficiently  that  it  cannot  pafs  into  the 
ureters. 

Sect.  XII.  Of  the  Urinary  Bladder. 

The  urinary  bladder  is  a membranous  and 
mufcular  bag  of  an  oblong  round ifh  fbape,  fitu- 
ated  in  the  pelvis,  between  the  os  pubis  and  in- 
teftinuin  re£tum  in  men,  and  between  the  os  pu-  | 
bis  and  uterus  in  women.  Its  upper  and  wideft 
part  is  ufnaSly  called  the  bottom.^  its  ifarrow  part 
the  neck  of  the  bladder ; the  former  only  is  co-  ij 
vered  by  the  peritonaeum.  - 

The  bladder  is  formed  of  three  coats,  connect- 
ed together  by  means  of  cellular  membrane. 
The  external  or  peritonaeal,  is  only  a partial  one,^" 
covering  the  upper  and  back  part  of  the  bladder. 
The  middle,  or  mufcular  coat,  is  compofed  of 
irritable,  and  of  courfe  mufcular  fibres,  which 
are  moft  collected  around  the  neck  of  the  blad- 
der, but  not  fo  as  to  form  a diftinCt  mufcle,  or 
fphinCter,  as  the  generality  of  anatomifts  have 
hitherto  fuppofed. 

The  inner  coat,  though  much  fmoother,  has 
been  faid  to  refemble  the,  villous  tunic  of  the  in- 
tefiines,  and  like  that  is  provided  with  a mu- 
cus, which  defends  it  againft  the  acrimony  of 
the  urine. 

It  will  be  eafily  conceived  from  what  has 
been  faid,  that  the  kidneys  are  two  glandular  bo- 
dies, through  which  a faline  and  excrementitious 

fluid 


Part  111.  OF  THE  ABDOMEN.  267 
fluid  called  urine  is  conftantly  filtering  firom  the 
mafs  of  blood. 

While  only  a fmall  quantity  of  urine  is  col- 
lected in  the  bladder,  it  excites  no  kind  of  un- 
eafinefs  ; but  when  a greater  quantity  is  accu- 
mulated, fo  that  the  bladder  is  dillended  in  a cer- 
tain degree,  it  excites  in  us  a certain  fenfation, 
which  brings  on  as  it  were  a voluntaiy  contrac- 
tion of  the  bladder  to  promote  its  difcharge. — 
But  this  contraction  is  not  effeCled  by  the  muf- 
cular  fibres  of  the  bladder  alone  : for  all  the  ab- 
dominal mufcles  contract  in  obedience  to  our 
will,  and  prefs  downwards  all  the  vifcera  of  the 
lower  belly  ; and  thefe  powers  being  united,  at 
length  overcome  the  refiftance  of  the  fibres  fur- 
rounding  the  neck  of  the  bladder,  which  dilates 
and  affords  a pafTage  to  the  urine  through  the 
urethra. 

The  frequency  of  this  evacuation  depends  on 
the  quantity  of  urine  fecreted  ; on  the  degree  of 
acrimony  it  pofTeffes  ; on  the  fize  of  the  bladder, 
and  on  its  degree  of  fenfibility. 

The  urine  varies  much  in  its  colour  and  con- 
tents. Thefe  varieties  depend,  on  age,  fex,  climate, 
iiet,  and  other  circumftances.  In  infants  it  is  ge- 
aerally  a clear  wateiy  fluid,  without  fmell  or 
:afte.  As  we  advance  in  life,  it  acquires  more 
:olour  and  fmell,  and  becomes  more  impregnat- 
’d with  falts.  In  old  people  it  becomes  flill  more 
icrid  and  fetid. 


In 


268  OF  THE  ABDOMEN.  Part  III. 

In  a healthy  ftate  it  is  nearly  of  a ftraw  co- 
lour.— After  being  kept  for  fome  time,  it  depp- 
lites  a tartarous  matter,  which  is  found  to  be 
compofed  chiefly  of  earth  and  fait,  and  foon  in- 
crufts the  Tides  of  the  veflTel  in  which  it  is  con- 
tained. While  this  reparation  is  taking  place, 
appearances  like  minute  fibres  or  threads  of  a 
whitifli  colour,  may  be  feen  in  the  middle  of  the 
urine,  and  an  oily  fcum  obferved  floating  on  its 
furface.  So  that  the  moft  common  appearances 
of  the  urine  are  fuflicient  to  afcertain  that  it  is  a 
watery  fubftance,  impregnated  with  earthy,  fa- 
line,  and  oily  particles. 

The  urine  is  not  always  voided  of  the  fame 
colour  and  confiftence ; for  thefe  arc  found  te 
depend  on  the  proportion  of  its  watery  part  to 
that  of  its  other  conftituent  principles. — Its  co- 
lour and  degree  of  fluidity  feem  to  depend  of) 
the  quantity  of  faline  and  inflammable  particle^ 
contained  in  it : fo  that  an  increafed  proportion 
of  thofe  parts  will  conftantly  give  the  urine  ^ 
higher  colour,  and  add  to  the  quantity  of  fedi 
ment. 

The  variety  in  the  appearance  of  the  urine 
depends  on  the  nature  and  quantity  of  folid  anfji 
fluid  aliment  we  take  in  ; and  it  is  likewife  occa 
fioned  by  the  different  ftate  of  the  urinary  veflTelf 
by  which  we  mean  the  channels  through  whid: 
it  is  fepai'ated  from  the  blood,  and  conveye 
through  the  pelvis  into  the  ureters.  The  caufe 
of  calculous  concretions  in  the  urinary  palfageij 

aij 


Part.  Ill  GF  THE  ABDOMEN.  269 
sure  to  be  looked  for  in  the  natural  conftitution  of 
the  body,  mode  of  life,  &c. 

It  having  been  obferved,  that  after  drinking 
any  light  wine  or  Spa  water,  it  very  foon  pafled 
off  by  urine,  it  has  been  fuppoled  by  fome,  that 
the  urine  is  not  altogether  conveyed  to  the  blad- 
der by  the  ordinary  courfe  of  circulation,  but 
that  there  muft  certainly  exift  fome  other  fhorter 
means  of  communication,  perhaps  by  certain 
veflels  between  the  ftomach  and  the  bladder,  or 
by  a retrograde  motion  in  the  lymphatics.  But 
it  is  certain,  that  if  we  open  the  belly  of  a dog, 
prefs  out  the  urine  from  the  bladder,  pafs  a liga- 
ture round  the  emulgent  arteries,  and  then  few 
up  the  abdomen,  and  give  him  even  the  moll 
diuretic  liquor  to  drink,  the  ftomach  and  other 
channels  will  be  diftended  with  it,  but  not  a drop 
of  urine  will  be  found  to  have  pafled  into  the 
bladder ; or  the  fame  thing  happens  when  a liga- 
ture is  thrown  round  the  two  ureters.  This  ex- 
periment then  feems  to  be  a fufficient  proof,  that 
all  the  urine  we  evacuate,  is  conveyed  to  the 
kidneys  through  the  emulgent  arteries,  in  the 
manner  we  have  defcrihed. — It  is  true,  that  wine 
and  other  liquors  promote  a fpeedy  evacuation  of 
urine  : but  the  difcharge  feems  to  be  merely  the 
effe<ft  of  the  ftimulds  they  occafion ; by  which  the 
bladder  and  urinary  parts  arefolicited  to  a more  co- 
pious difcharge  of  the  urine,  which  was  before  in 
the  body,  and  not  immediately  of  that  which  was 
laft  drank  ; and  this  increafed  difcharge,  if  the 

fupply 


270  OF  THE  ABDOMEN.  Part  III. 
Eupply  is  kept  up,  will  continue : nor  will  this 
appear  wonderful,  if  we  confider  the  great  capa- 
city of  the  veffels  that  go  to  the  kidneys ; the 
conftant  fupply  of  frefh  blood  that  is  elTential  to 
health  ; and  the  rapidity  with  which  it  is  incef- 
fandy  circulated  through  the  heart  to  all  parts  of 
the  body. 

Sect.  XIII.  Of  Digefion. 

W E are  now  proceeding  to  fpeak  of  digefion^ 
which  feems  to  be  introduced  in  this  place  with 
propriety,  after  a defcription  of  the  abdominal 
vifcera,  the  greater  part  of  which  contribute  to 
this  fundlion.  By  digefion  is  to  be  underftood, 
the  changes  the  aliment  undergoes  for  the  forma- 
tion of  chyle  ; — thefe  changes  are  effedted  in  the 
mouth,  ftomach,  and  fmall  inteftines. 

The  mouth,  of  which  every  body  has  a ge- 
neral knowledge,  is  the  cavity  between  the  two 
jaws,  formed  anteriorly  and  laterally  by  the  lips, 
teeth,  and  cheeks,  and  terminating  pofceriorly  in 
the  throat. 

The  lips  and  cheeks  are  made  up  of  fat  and 
mufcles,  covered  by  the  cuticle,  which  is  conti- 
nued over  the  whole  inner  furface  of  the  mouth, 
like  a fine  and  delicate  membrane. — Belide  this 
membrane,  the  infide  of  the  mouth  is  furniilied 
with  a fpongy  and  very  vafcular  fubftance  called 
gums ^ by  means  of  which  the  teeth  are  fe- 
cured  in  their  fockets.  A fimilar  fubftance  covers 
the  roof  of  the  mouth,  and  forms  what  is  called 

the 


Part  III.  OF  THE  ABDOMEN.  271 
the  velum  pendulum  palati^  which  is  fixed  to  the 
extremity  of  the  arch  formed  by  the  ofla  max- 
illaria  and  ofla  palati,  and  terminates  in  a foft, 
fmall,  and  conical  body,  named  uvula ; which 
appears,  as  it  were,  fufpended  from  the  middle 
of  the  arch  over  the  bafis  of  the  tongue. 

The  velum  pendulum  palati  performs  the  of- 
fice of  a valve  between  the  cavity  of  the  mouth 
and  the  pharynx,  being  moved  by  feveral  muf- 
cles  (f). 

The  tongue  is  compofed  of  feveral  mufcles 
(g)  which  enable  it  to  perform  a variety  of  mo- 
tions for  the  articulation  of  the  voice  ; for  the 
purpofes  of  maftication;  and  for  conveying  the 
aliment  into  the  pharynx.  Its  upper  part  is  co- 
vered with  papillse,  which  conftitute  the  organ 
of  tafte,  and  are  eafily  to  be  diftinguifhed  ; it  is 
covered  by  the  fame  membrane  that  lines  the  in- 
fide  of  the  mouth,  and  which  makes  at  its  infe- 
rior part  towards  its  bafis  a reduplication  called 
freenum. 

Pofteriorly,  under  the  vel,um  palati,  and  at 
the  bafis  of  the  tongue,  is  the  pharynx  : which 
is  the  beginning  of  the  oefophagus,  ftretched  out 
every  way,  fo  as  to  refemble  the  top  of  a fun- 


(f)  Thefe  are  the  drcmnflexus  palati,  le\'ator  palati  mol- 
lis, palato-pharyngaeus  conftriftor  iflhmi  faucium  and  azyjros 
uvulas. 

(g)  Thefe  are,  the  genio-gloJTas,  hyo-gloffus,  lingualis,. 
»nd  ftylo-gloflTos; 


272  OF  THE  ABDOMEN.  Part  III. 
nel,  through  which  the  aliment  paffes  into  the 
ftomach. 

The  mouth  has  a communication  with  the 
noftrils  at  its  pofterior  and  upper  part ; with  the 
ears,  by  the  Euftachian  tubes ; with  the  lungs, 
by  means  of  the  laiynx  ; and  with  the  ftomach, 
by  means  of  the  osfophagus. 

The  pharynx  is  conftantly  moiftened  by  a 
fluid,  fecreted  by  two  confiderable  glands  called 
the  tonfils^  one  on  each  fide  of  the  velum  palati. 
Thefe  glands,  from  their  fuppofed  refemblance 
to  almonds,  have  likewife  been  called 
dalis. 

The  mouth , is  moiftened  by  a confiderable 
quantity  of  faliva,  lliis  fluid  is  derived  from 
the  parotid  ghmds ; a name  which  by  its  ety- 


one  common  channel,  that  runs  over  the  cheek, 
and  piercing  the  buccinator  mufcle,  opens  into 
the  mouth  on  each  fide,  by  an  orifice  into  which 
a briftle  may  be  eafily  introduced. — Befides 
thefe,  the  maxillary  glands,  which  are  placed 
near  the  inner  furface  of  the  angle  of  the  lower 
jaw  on  each  fide  ; the  fublingual  glands,  which 
are  fituated  at  the  root  of  the  tongue  : the  glands 
of  the  palate,  which  are  feated  in  the  velum  pa- 
lati ; 


mology  points  out  their  fituation  to  be  near  th^ 
ears.  They  are  two  in  number,  one  on  eacly 
fide  under  the  os  malae  : and  they  are  of  the  com 
glomerate  kind  ; being  formed  of  many  fmaller^ 
glands,  each  of  which  fends  out  a very  fmall  ex-^ 
cretory  du<ft,  which  unites  with  the  reft,  to  form 


Part  III.  OF  THE  ABDOMEN.  273 
lati ; and  thofe  of  the  cheeks,  lips,  &c.  together 
with  many  other  lefs  confiderable  ones, — pour 
the  fahva  into  the  mouth  through  their  feveral 
excretory  du(3;s. 

The  faiiva,  like  all  the  other  humours  of  the 
body,  is  found  to  be  different  in  different  peo* 
pie ; but  in  general,  it  is  a limpid  and  infipid 
fluid,  without  fmell  in  healthy  fubje£ts  ; and  thefe 
properties  would  feem  to  prove  that  it  contains 
very  few  faline  or  inflammable  particles. 

The  ufes  of  the  faiiva  feem  to  be  to  moiften 
and  lubricate  the  mouth,  and  to  adift  in  reducing 
the  aliment  into  a foft  pulp  before  it  is  conveyed 
into  the  ftomach. 

The  variety  of  fimd;ions  which  are  conftant- 
ly  performed  by  the  living  body,  muft  neceffa- 
rily  occafion  a continual  wafte  and  diffipation  of 
its  feveral  parts.  A great  quantity  is  every  day 
thrown  off  by  the  infenfible  perfpiration  and 
other  difcharges;  and  were  not  thefe  Ioffes 
conftantly  recruited  by  a frefh  fuppiy  of  chyle, 
the  body  would  foon  effe(ff  its  own  diffo- 
lutioru  But  nature  has  very  wifely  favour- 
ed us  with  organs  fitted  to  produce  fuch  a fup- 
piy ; and  has  at  the  fame  time  endued  us  with 
the  fenfations  of  hunger  and  third,  that  our  at- 
tention may  not  be  diverted  from  the  neceffary 
bufmefs  of  nutrition.  The  fenfation  of  hunger 
is  univerfally  known  ; but  it  would  perhaps  be 
difficult  to  defcribe  it  perfedlly  in  words.  It  may, 
however,  be  definedtobe  a certain  uneafy  fenfation 

S in 


^74  OF  THE  ABDOMEN.  Part  III. 

in  the  ftomach,  which  induces  us  to  wifli  for  fo- 
lid  food  ; and  which  likewife  ferves  to  point  out 
the  proper  quantity,  and  time  for  taking  it.  1 n 
dclcribing  the  ftomach,  mention  was  made  of  the 
gaftric  juice,  as  every  where  lubricating  its  inner 
coat.  This  humour  mixes  itfelf  with  the  aliment 
in  tlie  ftomach,  and  helps  to  prepare  it  for  its  paf- 
iage  into  the  inteftines  ; but  when  the  ftomach  is 
perfedly  empty,  this  fame  fluid  irritates  the  coats 
of  the  ftomach  itfelf,  and  produces  the  fenfation 
of  hunger. 

A certain  proportion  of  liquid  aliment  is 
required  to  aflift  in  the  procefs  of  digeftion, 
and  to  afford  that  moifture  to  the  body,  of  which 
there  isfuch  a conftant  difflpation. — Thirft  in- 
duces us  to  take  this  neceffary  fupply  of  drink; 
and  the  feat  of  this  fenfation  is  in  the  tongue, 
ftiuces,  and  oefophagus,  which  from  their  great 
fenfibility  are  required  to  be  kept  moift  : for 
though  the  fauces  are  naturally  moiftened  by  the 
mucus  and  falival  juices  ; yet  the  blood,  when 
deprived  of  its  watery  part  or  rendered  acrimo- 
nious by  any  natural  caufes,  never  fails  particu- 
larly to  afi’e(ft  thefe  parts,  and  the  whole  alimen- 
tary canal,  and  to  occafion  thirft. — This  is  the 
common  effed;  of  fevers  and  of  hard  labour,  by 
both  which  too  much  of  the  watery  part  of  the 
blood  is  diffipated. 

MaJUcatlon  and  deglutition.  It  has  been  ob- 
ferved,  that  the  aliment  undergoes  fome  prepa- 
tion  in  the  mouth  before  it  palfes  into  the  fto- 
mach ; 


Part  III.  OF  THE  ABDOMEN.  275 

mach  ; and  this  preparation  is  the  effeT  of  maf- 
tication.  In  treating  of  the  upper  and  lower 
jaws,  mention  was  made  of  the  number  and  ar- 
rangement of  the  teeth.  The  upper  jaw  was 
defcribed  as  being  immoveable  ; but  the  lovrer 
javr  was  fpoken  of  as  being  capable  of  eleva- 
tion  and  depreffion,  and  of  a grinding  motion. 
The  aliment,  when  firft  carried  into  the  mouth, 
is  preffed  between  the  teeth  of  the  two  jaws  by 
nvery  ftrong  and  frequent  motion  of  the  lower 
jaw  ; and  the  tongue  and  the  cheeks  aifi fling  in 
this  procefs,  continue  to  replace  the  food  be- 
tween the  teeth  till  it  is  perfeflly  divided,  and 
reduced  to  the  confiftence  of  pulp.  The  inci- 
fores  and  canini  divide  it  firft  into  fmaller  pieces, 
but  it  is  between  the  furfaces  of  the  dentes  mo- 
lares  by  the  grinding  motion  of  the  javr  that  the 
maftication  is  completed. 

During  this  procefs,  the  falival  glands  being 
gently  comprefled  by  the  contradlion  of  the  muf- 
cles  that  move  the  lower  jaw,  pour  out  their  ia- 
liva : this  helps  to  divide  and  break  down  the 
food,  which  at  length  becomes  a kind  of  pulp, 
and  is  then  carried  over  the  bafts  of  the  tongue 
into  the  fauces.  But  to  efteft  this  pafTage  into 
the  oefophagus,  it  is  necelTary  that  the  other 
openings  which  were  mentioned  as  having  a 
communication  with  the  mouth  as  well  as  the 
pharynx,  fliould  be  clofed  ; that  none  of  the  ali- 
ment, whether  folid  or  licjuid,  may  pafs  into 
them,  whilft  the  pharynx  alone  is  dilated  to  re- 

S 2 ceive 


276  OF  THE  ABDOMEN.  Part  III. 

ceive  It : — And  fuch  a difpofition  ailually  takes 
place  in  a manner  we  will  endeavour  to  de- 
fcribe. 

The  trachea  arteria,  or  windpipe,  through 
which  the  air  is  conveyed  to  the  lungs,  is  plac- ' 
ed  before  the  oefophagus-^in  the  a<T  of  fwailow- 
ing,  therefore,  if  the  larynx  (for  fo  the  upper 
part  of  the  trachea  is  called)  is  not  clofed,  the 
aliment  will  pafs  into  it  in  its  way  to  the  oefo- 
phagus.  But  this  is  prevented  by  a fmall  and 
very  elaftic  cartilage,  called  epiglottis^  which  is 
attached  only  to  the  fore-part  of  the  larynx  ; fo 
that  the  food  in  its  paifage  to  the  oefophagus  prefles 
down  this  cartilage,  which  then  covers  the  glot- 
tis or  opening  of  the  larynx  ; and  at  the  lame 
time  the  velum  palati  being  capable  of  fome  de- 
gree of  motion,  is  drawn  backwards  by  its  muf- 
cles,  and  clofes  the  openings  into  the  nofe  and 
the  Euftachian  tubes.— ^This,  however,  is  not 
all.  The  larynx,  which  being  compofed  of  car- 
tilaginous rings,  cannot  fail  in  its  ordinary  ftate 
to  comprefs  the  membranous  canal  of  the  eefo- 
piiagus,  is  in,  the  adt  of  deglutition  carried  for- 
wards and  upwards  by  mufcles  deftined  for  that 
purpofe  ; and  confequently  drawing  the  fore-' 
part  of  the  pharjmx  with  it,  that  opening  is  ful- 
ly dilated.  A¥hen  the  aliment  has  reached  the 
pharynx,  its  defcent  is  promoted  by  its  own  pro- 
per weight,  and  by  the  mufcular  fibres  of  the 
cefophagus,  which  continue  to  contradf  from 
above  downwards,  until  the  aliment  has  reach- 
ed 


Part  III.  OF  THE  ABDOMEN.  277 

ed  the  ftomach.  That  thefe  fibres  have  no  in- 
confiiderable  Ihare  in  deglutition,  any  perfon  may 
experience,  by  fwallowing  with  his  head  down- 
wards, when  the  defcent  of  the  aliment  xannot 
pofiTibly  be  effedted  by  its  weight. 

It  is  neceflary  that  the  noftrils  and  the  lungs 
Ihould  communicate  with  the  mouth,  for  the 
purpofes  of  fpeech  and  refpiration  : but  if  the 
moll  minute  part  of  our  food  happens  to  be  in- 
troduced into  the  trachea,  it  never  fails  to  pro- 
duce a violent  cough,  and  fometimes  the  moft 
alarming  fymptoms.  This  is  liable  to  happen 
when  we  laugh  or  fpeak  in  the  ad;  of  degluti- 
tion : the  food  is  then  faid  to  have  palfed  the 
wrong  way.  And  indeed  this  is  not  improper- 
ly exprelTed  : for  death  would  foon  follow,  if 
the  quantity  of  aliment  introduced  into  the 
trachea  Ihould  be  fufficient  to  obflrad  the  refpi- 
ration only  during  a very  fhort  time  ; or  if  the 
irritating  particles  of  food  flrould  not  be  thrown 
up  again  by  means  of  the  cough,  which  in  thefe 
cafes  very  feafonably  increafes  in  proportion  to 
the  degree  of  irritation. 

If  the  velum  palati  did  not  clofe  the  palfage  to 
the  noftrils,  deglutition  would  be  performed 
with  difficulty,  and  perhaps  not  at  all ; for  the  ali- 
ment would  return  through  the  nofe,  as  is  fome- 
times the  cafe  in  drinking.  Children,  from  a 
deficiency  in  this  velum  palati,  have  been  feen 
to  die  a few  hours  after  birth ; and  they  who 

from 


278  OF  THE  ABDOMEN.  Part  III. 

from  difeafe  or  any  other  caufes  have  not  this 
part  perfecT,  hvallow  with  difficulty. 

Idle  aliment  after  having  been  fufficiently  di- 
vided by  the  adlion  of  the  teeth,  and  attenuated 
by  the  faliva,  is  received  into  the  ftomach,  where 
it  is  dellined  to  undergo  a more  confiderable 
change. 

d'he  properties  of  the  aliment  not  being  much 
altered  at  its  firft  entrance  into  the  homach,  and 
before  it  is  thoroughly  blended  with  the  gaftric 
juice,  is  capable  of  irritating  the  inner  coat  of 
the  ftomach  to  a certain  degree,  and  occafions  a 
contradtion  of  its  two  orifices. — In  tliis  mem- 
branous bag,  furrounded  by  the  abdominal  vif- 
cera,  and  with  a certain  degree  of  natural  heat, 
the  aliment  undergoes  a conftant  agitation  by 
means  of  abdominal  mufcles  and  of  the  dia- 
phragm, and  likewife  by  a certain  contraction  or 
expanfion  of  the  mufcular  fibres  of  the  ftomach  f 
itfelf.  By  this  motion,  every  part  of  the  food'  " 
is  expofed  to  the  adtion  of  the  gaftric  juice,  which 
gradually  divides  and  attenuates  it,  and  prepares 
It  for  its  paflage  into  the  inteftines. 

Some  obfervations  lately  publiftied  by  Mr. 
Hunter  in  the  Philofophical  Tranfactions,  tend 
to  throw  confiderable  light  on  the  principles  of 
digeftion.  There  are  few  dead  bodies  in  which  |j 
the  ftomach,  at  its  great  end,  is  not  found  to  be 
in  fome  degree  digefted  (h).  Animals,  or  parts 

of 

(H)The  Abbe  Spallanzani,  who  has  lately  written  upon  Ji-  ij 
refiion,  finis,  frotn  a variety  of  experiments,  niaue  upon 

opukiri!’ 


Part  III.  OF  THE  ABDOMEN.  2jg 

of  animals,  poflefl'ed  of  the  living  principle, 
when  taken  into  the  ftomach,  are  not  in  the 
leaft  affedted  by  the  action  of  that  vifcus ; but 
the  moment  they  lofe  the  living  principle,  they 
become  fubjedt  to  its  digeftive  powers.  This 
feems  to  be  the  cafe  with  the  ftomach,  which  is 
enabled  to  refift  the  aftion  of  its  juices  in  the 
living  body  : but  when  deprived  of  the  living 
principle,  it  is  then  no  longer  able  to  refift  the 
powers  of  that  menftruum,  which  it  had  itfelf 
formed  for  the  digeftion  of  its  contents  ; the  pro- 
cefs  of  digeftion  appearing  to  be  continued  after 
death.  This  is  confirmed  by  what  happens  in 
the  ftomachs  of  fifties  : they  frequently  fwal- 
low,  without  maftication,  fifh  which  are  larger 
than  the  digefting  parts  of  their  ftomach  can 

contain ; 

quadrupeds,  birds,  and  fifnes,  that  digeftion  goes  on  for 
Jbme  time  after  death,  though  far  lefs  confiderable  than  in 
living  animals,  or  at  leaft  promotes  it  in  a m.uch  greater  de- 
gree. He  found  alfo,  that  when  the  ftomach  was  cut  out  of 
the  body,  it  had  fomewhat  of  the  power  of  digeftion,  though 
this  was  trifling  when  compared  with  that  which  took  place 
when  the  ftomach  was  left  in  the  body.  In  not  one  ol  the 
animals  was  the  great  curvature  of  the  ftomach  diflblved, 
or  much  eroded  after  death.  There  was  often  a little  ero- 
fion,  efpecially  in  different  filhes  ; in  which,  when  he  had 
cleared  the  ftomach  of  its  contents,  the  internal  coat  was 
wanting.  In  other  animals  there  was  only  a flight  excoria- 
tion ; and  the  injury  in  all  of  them  was  at  the  inferior  part, 
or  great  curvature.  The  cc'ats  of  the  ftomach  fuffer  lefs  af- 
ter death  than  flefh,  or  part  of  the  ftomach  of  fimilar  animals 
put  into  it:  the  author  affigns  as  a reafon  for  this,  that  thefe 
bodies  are  invefted  on  all  fides  by  the  gaftric  fluid,  whereas 
it  only  afls  on  the  internal  furf.ice  of  the  ftomach. 


28o  of  the  abdomen.  Part  III. 

contain ; and  in  fuch  cafes,  that  part  which  is 
taken  into  the  ftomach  k more  or  lefs  diffolved, 
while  that  part  which  remains  in  the  oefo- 
phagus  is  perfectly  found ; and  here,  as  well 
as  in  the  human  body,  the  digefting  part  of 
the  ftomach  is  often  reduced  to  the  fame 
ftate  as  the  digefted  part  of  the  food.  Thefe 
appearances  tend  to  prove,  that  digeftion  is  not 
effed:ed  by  a mechanical  power,  by  contractions 
of  the  ftomach,  or  by  heat ; but  by  a fluid  fe- 
creted  in  the  coats  of  the  ftomach,  which  is 
poured  into  its  cavity,  and  there  animalizes  the 
food,  or  alTimijates  it  to  the  nature  of  the  blood. 

From  feme  late  experiments  by  M.  Sage*,  it 
appears,  that  inflammable  air  has  the  property 
of  deftroying  and  dilfolving  the  animal  texture  : 
-and  as  we  fwallow  with  the  fubftances  which 
ferve  us  for  food  a great  quantity  of  atmofphe- 
rical  air,  M.  Sage  thinks  it  poflible,  that  de- 
plogifticated,  which  is  its  principle,  may  be  con- 
verted in  the  ftomach  into  inflammable  air,  or 
may  modify  into  inflammable  air  a portion  of 
the  oily  fubftance  which  is  the  principle  of  ali- 
ments. In  this  cafe,  would  not  the  inflammable 
air  (he  afxs),  by  diffolving  our  food,  facilitate 
its  converfion  into  chyle  ? 

Be  this  as  it  may,  the  food,  after  having  re- 
mained one,  twOj  or  three  hours  in  the  ftomach, 

is 

Hift.  Cie  I’Academie  ro3'alc  des  Sciences,  &c.  pour  1 78.5, 
rr=em.  i c. 


Part  III.  OF  THE  ABDOMEN.  281 

is  converted  into  a greyifli  pulp,  which  is  ufual- 
ly  called  chynius^  a word  of  Greek  etymology, 
fignifyingy^/V^,  and  fome  few  milky  or  chylous 
particles  begin  to  appear. — But  the  term  of  its 
refidence  in  this  bag  is  proportioned  to  the  na- 
ture of  the  aliment,  and  to  the  ftate  of  the  fto- 
mach  and  its  juices.  The  thinner  and  more 
perfectly  digefted  parts  of  the  food  pafs  by  a lit- 
tle at  a time  into  the  duodenum,  through  the  py- 
lorus, the  fibres  of  which  relax  to  afford  it  a paf- 
fage  ; and  the  groffer  and  lefs  digefted  particles 
remain  in  the  ftomach,  till  they  acquire  a fuffi- 
cient  fluidity  to  pafs  into  the  inteftines,  where 
the  nature  of  the  chymus  is  perfectly  changed. 
The  bile  and  pancreatic  juice  which  flow  into  the 
duodenum,  and  the  mucus,  which  is  every 
wli.rc  d'.  led  from  the  furface  of  the  inteftines, 
mix  themlelves  vfith  the  alimentary  pulp,  which 
they  ftill  farther  attenuate  and  diffolve,  and  in- 
to which  they  feem  to  infufe  new  properties. 

Two  matters  very  different  from  each  other 
in  their  nature  and  deftination,  are  the  refult  of 
this  combination. — One  of  thefe,  which  is  com- 
pofed  of  the  liquid  parts  of  the  aliment,  and  of 
fome  of  its  more  folid  particles,  extremely  di- 
vided and  mixed  with  the  juices  we  have  de- 
fcribed,  conftitutes  a very  mild,  fweet,  and 
whitifh  fluid,  refembling  milk,  and  diftinguifh- 
ed  by  the  name  of  chyle.  This  fluid  is  abforb- 
ed  by  the  ladleal  veins,  which  convey  it  into 
the  circulation,  where,  bv  being  affimilated  into 

the 


2S2  OF  THE  ABDOMEN.  Part  III. 

the  nature  of  blood,  it  affords  that  fupply  of  nu- 
trition which  the  continual  wafte  of  the  body  is 
found  to  require. — The  other  is  the  remains  of 
the  alimentary  mafs  deprived  of  all  its  nu- 
tritious particles,  and  containing  only  fuch  parts 
as  were  rejected  by  the  abforbing  mouths  of  the 
ladfeals.  This  gtoffer  part,  called  the  faces ^ 
paffes  on  through  the  courfe  of  the  inteftines,  to 
be  voided  at  the  anus,  as  will  be  explained  here- 
after ; for  this  procefs  in  the  oeconomy  cannot 
be  well  underftood  till  the  motion  of  refpiration 
has  been  explained.  But  the  ftrudlure  of  the 
intePdncs  is  a fubjcd;  which  may  be  properly 
ddcribed  in  this  })lace,  and  defcrves  to  be  at- 
tended to. 

It  has  been  already  obferved,  that  the  intefli- 
nal  canal  is  five  or  fix  times  as  long  as  the  body, 
and  that  it  forms  many  circumvolutions  in  the 
cavity  of  the  abdomen,  which  it  traverfes  from 
the  right  to  the  left,  and  again  from  the  left  to 
the  right  : in  one  place  defcending,  and  in  ano- 
ther extending  itfelf  upwards.  It  was  noticed 
likewife,  that  the  inner  coat  of  the  inteftines,  by 
being  more  capacious  than  their  exterior  tunics, 
formed  a multitude  of  plaits  placed  at  a certain 
diftance  from  each  other,  and  called  valvula  con- 
■nlventcs.  Now  this  difpofition  v;ill  be  found  to 
afford  a farther  proof  of  that  divine  wifdom,  which 
the  anatcmift  and  phyiiologift  cannot  fail  to  dif- 
< over  in  ail  their  purfuits. — For  if  the  intefti- 
nal  canal  was  much  Ihorter  than  it  naturally  is  ; 
if  inftcad  of  the  prcfent  circumvolutions  it  pafi- 

cd 


Part  III.  OF  THE  ABDOMEN.  283 

ed  in  a dire£t  courfe  from  the  ftomach ; and  if 
its  inner  furface  was.  fmooth  and  deftitute  of 
valves  ; the  aliment  would  confequently  pafs 
with  great  rapidity  to  the  anus,  and  fufficient 
time  would  be  wanting  to  aflimilate  the  chyle, 
and  for  the  necefl'ary  abforption  of  it  into  the 
ladteals  ; lb  that  the  body  would  be  deprived  of 
the  fupply  of  nutrition,  which  is  fo  elTential  to 
life  and  health  ; but  the  length  and  circumvo- 
lutions of  the  inteftines,  the  inequality  of  their 
internal  furface,  and  the  courfe  of  the  aliment 
through  them,  all  concur  to  perfect  the  fepara- 
tion  of  the  chyle  from  the  feces,  and  to  afford 
the  necelfary  nourilhment  to  the  body. 

Sect.  XIV.  Of  the  Courfe  of  the  Chyle ^ a7id  of 
the  Lymphatic  S \fem. 

An  infinite  number  of  very  minute  velfels, 
called  the  laCeal  veins ^ arife  like  net-work  from 
the  inner  furface  of  the  inteftines,  (but  princi- 
pally from  the  jejunum  and  illump  which  are 
diftendedto  imbibe  the  nutritious  fluid  or  chyle. 
Thefe  velfels,  which  were  difcovered  by  Afel- 
lius  in  1622  (i),  pafs  obliquely  through  the 

coats 

(i)  Wc  are  informed  by  Galen,  that  the  lafteals  had  been 
hen  in  kids  by  Eraliftratns,  who  confidered  them  as  arteries 
tarrying  a milky  fluid:  but  from  the  remote  time  in  vthich 
he  lived,  they  do  not  fecm  to  have  been  noticed  till  they  were 
dilcovered  in  a living  dog  by  Afelllus,  who  denominated  them 
lacteah^  and  confidered  tliem  as  ferving  to  convey  the  chyle 
from  the  inttfrines  to  the  liver  ; for  before  the  difcovery  of 
the  thoracic  duct,  the  ufe  of  the  liver  was  univerfally  fup- 


284  OF  THE  ABCOMEN.  Pai?t  III. 

coats  of  the  inteftine,  • and  running  along  the 
mefentery,  unite  as  they  advance,  and  form 
larger  branches,  all  of  which  pafs  through  the 
mefenteric  or  conglobate  glands,  which  are  very 
numerous  in  the  human  fubjedt.  As  they  run 
between  the  inteftines  and  thefe  glands,  they 
are  ftyled  vencd  laElea  primis  generis  : but  after 
leaving  thefe  glands,  they  are  found  to  be  lefs 
numerous,  and  being  increafed  in  fize,  are  then 
called  vena  laEiea  Jeaindi  generis^  which  go  to 
depofit  their  contents  in  the  thoracic  duB^  through 
which  the  chyle  is  conveyed  into  the  blood. 

This  thoracic  duB  begins  about  the  lower  part 
of  the  firft  vertebra  lumborum,  from  whence  it 
pafles  up  by  the  fide  of  the  aorta,  between  that 
and  the  vena  azygos,  clofe  to  the  vertebrse,  be- 
ing covered  by  the  pleura.  Sometimes  it  is  found 
divided  into  branches  ; but  they  ufually  unite 
again  into  one  canal,  which  opens  into  the  left 
fubclavian  vein,  after  having  run  a little  way  in 
an  oblique  courfe  between  its  coats.  The  fub- 
clavian vein  communicates  with  the  vena  cava, 
which  ptlTes  to  the  right  auricle  of  the  heart. 

The 

pofed  to  be  that  of  converting  the  chyle  into  blood.  But  the 
difcovery  of  the  thoracic  dudl  by  Pecquet,  not  long  after, 
corrected  this  error.  Pecquet  very  candidly  confeffes  that 
this  difcovery  acccidentally  arofe  from  his  obferving  a 
■white  fluid,  mixed  with  the  blood,  flowing  out  of  the 
vena  cava,  after  he  had  cut  off  the  heart  of  a living  dog  5 
which  he  fufpcdted  to  be  chyle,  and  afterwards  traced  to  its 
fource  from  the  thoracic  duft  : this  dudf  had  been  feen  near 
an  hundred  years  before  in  ahorfeby  Euflachius,  who  fpeaks 
of  it  as  a vein  of  a particular  ftruff'are,  but  without  know- 
ing any  thing  of  its  termination  or  ule. 


Part  III.  OF  THE  ABDOMEN.  285 

The  lower  part  of  this  dudt  being  ufualiy 
larger  than  any  other  part  of  it,  has  been  nam- 
ed receptaculum  chyli^  or  P-ecquef  s receptacle^  in 
honour  of  the  anatomift  who  firft  diicovered  it 
in  1 65 1 . In  fome  quadrupeds,  in  turtle  and  in 
filh,  this  enlargement  * is  more  confiderable  in 
proportion  to  the  fize  of  the  du<St,  than  it  ufu- 
ally  is  in  the  human  fubjeft,  where  it  is  not  com- 
monly found  large  enough  to  merit  the  name  of 
receptaculum. 

Opportunities  of  obferving  the  ladteals  in  the  • 
human  fubje£t  do  not  often  occur ; but  they 
may  be  ealily  demonftrated  in  a dog  or  any  other 
quadruped  that  is  killed  two  or  three  hours  af- 
ter feeding  upon  milk;  for  then  they  appear  fill- 
ed with  white  chyle. 

But  thefe  la&eals  which  we  have  defcribed,  as 
palling  from  the  inteftines  through  the  mefen- 
tery  to  the  thoracic  du6t,  compofe  only  a part  of 
a fyftem  of  veflels  which  perform  the  office  of 
abforption^  and  which  conftitute,  Math  their 
common  trunk,  the  thoracic  du<ff,  and  the 
conglobate  glands  that  are  difperfed  through  the 
body,  what  may  be  ftyled  the  lymphatic  fyjlem. 

So  that  what  is  faid  of  the  ftrudlure  of  one  of 
thefe  feries  of  veflels  may  very  properly  be  ap- 
plied to  that  of  the  other. 

The  lymphatics  veins  (k)  are  minute  pellu- 
cid 

* Hcwfon’s  Exp.  Inq.  Part  IL 

(k)  The  arteries  in  their  courfe  through  the  body  becom- 
ing gradually  too  minute  to  admit  the  red  globule«  of  the 

blood. 


286  OF  THE  ABDOMEN.  Part  BL 

cid  tubes,  which  like  the  ladteals,  dired;  their 
courle  towards  the  centre  of  the  body,  where 
they  pour  a colourlefs  fluid  into  the  thoracic  dud. 
The  lymphatics  from  all  the  lower  parts  of  the 
body  gradually  unite  as  they  approach  this  dud, 
into  which  they  enter  by  three  or  four  very  large 
trunks,  that  leem  to  form  the  lov/er  extremity 
of  this  canal,  or  reccptaculum  chyli^  wliich  may 
be  ccnfidered  as  the  great  trunk  of  the  lympha- 
tic fyftem.  The  ladeals  open  into  it  near  thc; 
fame  place;  and  the  lymphatics,  from  a large 
lharc  of  the  upper  parts  of  the  body,  pour  their 
lymph  into  different  parts  of  this  dud  as  it  runs 
upwards,  to  terminate  in  the  left  fubclavian  vein. 
The  lymphatics  from  the  right  fide  of  the  neck, 
thorax,  and  right  arm,  &c.  terminate  in  the 
fight  fubclavian  vein. 

As  the  lymphatics  commonly  lie  clofe  to  the 
large  blood-veflels,  a ligature  pafTed  round  the 

crural 

blood,  hav'e  then  been  flyled  capillary  or  lymphatic  arteries. 
The  velFels  which  are  here  deferibed  as  conlUtuting  the  lym- 
phatic fyftem,  were  at  firlt  fuppofei  to  be  continued  from 
thofe  arteries,  and  to  convey  back  the  lymph,  either  into  the 
red  veins  or  the  thoracic  duft  j the  ofnee  of  abforption  hav- 
ing been  attributed  to  the  red  veins.  But  we  know  that  the 
lymphatic  veins  are  not’ continuations  of  the  lymphatic  arteries^ 
but  that  they  conrtitute  the  ahforbent  fyjlcm.  There  are  ftill, 
however,  fome  very  refpeftable  names  among  the  anatomifls 
of  the  prefent  age,  who  contend,  that  the  red  veins  aA  like- 
wife  as  abforbents  : — but  it  Items  to  have  been  clearly  prov- 
ed, that  the  red  veins  do  ablbrb  no  where  but  in  the  caver- 
n'.)us  cells  of  the  penis,  the  ereffion  of  which  is  occafioned 
by  a diffenfion  of  thofe  cells  with  arterial  blood. 


Part  III.  OF  THE  ABDOMEN.  2S7 

crural  artery  in  a living  animal,  by  including  the 
lymphatics,  will  occafion  a diftenfion  of  thefe 
velTels  below  the  ligature,  fo  as  to  clemonfti'ate 
them  with  eafe  ; and  a ligature  paffed  round  the 
thoracic  du(T,  inftantly  after  killing  an  animal, 
will,  by  flopping  the  courfe  of  its  contents  into 
the  fubclavian  vein,  diflend  not  only  the  la(!deals, 
but  alfo  the  lymphatics  in  the  abdomen  and 
lower  extremities,  with  their  natural  fluids  (l). 

The  coats  of  thefe  veffels  are  too  thin  to  be 
feparated  from  each  other  ; but  the  mercury  they 
are  capable  of  fuflaining,  proves  them  to  be  ve- 
ry flrong  ; and  their  great  power  of  contraftion, 
after  undergoing  confiderable  diflenfion,  toge- 
ther with  the  irritability  with  which  Baron  Hal- 
ler found  them  to  be  endued  feems  to  render 
it  probable,  that  like  the  blood-veffels,  they  have 
a mufcular  coat. 

The  lymphatics  are  nouriflied  after  the  fame 
manner  as  all  the  other  parts  of  the  body.  For 
even  the  mofl  minute  of  thefe  veiTels  are  pro- 
bably fupplied  with  flill  more  minute  arteries 
and  veins.  This  feems  to  be  proved  by  the  in- 
flammation of  which  they  are  fufceptible ; and 

the 

(l)  In  the  dead  body  they  may  be  eafdy  demonftrated  bv 
opening  the  artery  ramifying  through  any  vifcus,  as  in  the 
fpleen,  for  inftance,  and  then  throwing  in  air ; by  which 
the  lymphatics  will  be  diflended.  One  of  them  may  be 
punftured,  and  mercury  introduced  into  it  through  a blow- 
pipe. 

* Sur  le  movement  dll  fang  Ex.  29  c,  298, 


288  OF  THE  ABDOMEN.  Part  Ilf. 
the  painful  fwellings  which  fometimes  take  place 
in  lymphatic  veflels,  prove  that  they  have  nerves 
as  well  as  blood-veflels. 

Both  the  la(Teals,  lymphatics,  and  thoracic 
dudt,  are  furnilhed  with  valves,  which  are  much 
more  common  in  thefe  veflels  tlian  in  the  red 
veins.  Thefe  valves  are  ufually  in  pairs,  and 
ferve  to  promote  the  courfe  of  the  chyle  and 
lymph  towards  the  thoracic  duct,  and  to  pre- 
vent its  return.  Mention  has  been  made  of  the  j:  J 
glands,  through  which  the  ladeals  pafs  in  theif^; ,! 
courfe  through  the  mefentery  ; and  it  is  to  be  ob- 
ferved,  that  the  lymphatics  pafs  through  fimiiar^ 
glands  in  their  way  to  the  thoracic  du(T.  The^^^ 
glands  are  all  of  a conglobate  kind,  but  the 
changes  which  the  chyle  and  lymph  undergo  ini 
their  paffage  through  them,  have  not  yet  been' 
afceitained. 

The  lymphatic  vejfds  begin  from  furfaces  and^ 
cavities  in  all  parts  of  the  body  as  ahforbents.  ^ 
This  is  a fadl  now  univerfally  allowed  ; but 
how  the  fluids  they  abforb  are  poured  into  thofe ' 
carnties,  is  a fubjedt  of  controverfy.  The  con- 
tents of  the  abdomen,  for  inRance,  were  de-,^ 
fcribed  as  being  conftantly  moiftened  by  a very-  j 
thin  watery  fluid.  The  fame  thing  takes  place  M 
in  the  pericardium,  pleura,  and  all  the  other  ca-.^ 
vities  of  the  body,  and  this  wateiy  fluid  is  the  ^ 
ly?nph.  But  whether  it  is  exhaled  into  thofe,.jj^ 
cavities  through  the  minute  ends  of  arteries,  or 
tranfuded  through  their  coats,  are  the  points  in  : , 

2 difpute. 


Part  III.  OF  THE  ABDOMEN.  289 
difpute.  We  cannot  here  be  permitted  to  re- 
late the  many  ingenious  arguments  that  have 
been  advanced  in  favour  of  each  thefe  opinions ; 
nor  is  it  perhaps  of  confequence  to  our  prefent 
purpofe  to  enter  into  the  difpute.  It  will  be  fuffi- 
cient  if  the  reader  can  form  an  idea  of  what  the 
lymph  is,  and  of  the  manner  in  which  it  is  ab- 
forbed. 

The  lymph ^ from  ife  tranlparency  and  want  of 
colour,  would  feem  to  be  nothing  but  water ; 
and  hence  the  firftdifcoverers  of  thefe  veffels  ftiled 
them  duSlus  aqiioji : but  experiments  prove,  that 
the  lymph  of  an  healthy  animal  coagulates  by 
being  expofed  to  the  air,  or  a certain  degree  of 
heat,  and  likewife  by  being  fulfered  to  reft;  feem- 
ing  to  agree  in  this  property  with  that  part  of  the 
blood  called  the  coagulable  lymph. — This  proper- 
ty of  the  lymph  leads  to  determine  its  life,  in 
moiftening  and  lubricating  the  feveral  cavities  of 
the  body  in  which  it  is  found  ; and  for  which, 
by  its  gelatinous  principle,  it  feems  to  be  much, 
better  calculated  than  a pure  and  watery  fluid 
would  be,  for  fuch  it  has  been  fuppofed  to  be  by 
fome  anatomifts. 

The  mouths  of  the  lymphatics  and  laBeah\ 
by  acting  as  capillary  tubes,  feem  to  abforb  the 
lymph  and  chyle  fomewhat  in  the  fame  manner 
as  a capillary  tube  of  glafs,  when  put  into  a 
bafon  of  water,  is  enabled  to  attrad;  the  wa- 
ter into  it  to  a certain  height,  but  it  is  pro- 
bable that  they  likewife  polfefs  a living  power, 

T wdiich 


290  OF  THE  ABDOMEN.  Part  III. 

which  affifts  in  performing  this  office.  In 
the  human  body  the  lymph  or  the  chyle^  is  pro- 
bably conveyed  upon  this  principle  as  far  as  the 
hrft  pair  of  valves,  which  feem  to  be  placed  not 
far  from  the  orifice  of  the  abforbing  veffel,  whe- 
ther lymphaiic  or  laSleaJ : and  the  fluid  will  then 
be  propelled  forwards,  by  a continuation  of  the 
abfoiyition  at  the  orifice.  But  this  does  not  feem 
to  be  the  only  inducemeift  to  its  progrefs  to- 
wards the  thoracic  dud; ; thefe  veffels  have  pro- 
bably a mufcular  coat,  which  may  ferve  to  prefs 
the  fluid  forwards  from  one  pair  of  valves  to  ano- 
ther; and  as  the  large  lymphatic  veflTels  and  the 
thoracic  dud  are  placed  clofe  to  the  large 
arteries,  which  have  a confiderable  pulfa- 
tion,  it  is  reafonable  to  fuppofe,  that  they  de- 
rive fome  advantage  from  this  fituation. 

Sect.  XV.  Of  the  Generative  Organs  ; of  Con- 
ception &c. 

§ I,  The  Male  Organs, 

The  male  organs  of  generation  have  beeri 
ufually  divided  into  the  parts  which  ferve  to  pre- 
pare the  femen  from  the  blood,  and  thofe  which 
are  diftended  to  convey  it  into  the  womb.  But 
it  feems  to  be  more  proper  to  diftinguilh  them 
into  preparing y the  containing y and  the  ex- 

pelling parts, which  are  the  different  offices  of  the 
tefesy  the  veficula  feminaksy  and  the  penis ; and, 

this 


Part  III.  . OF  THE  ABDOMEN.  2gi 

this  is  the  order  in  which  we  propofe  to  defcribe 
them. 

The  teftes  are  two  glandular  bodies,  ferving 
to  fecrete  the  femen  from  the  blood.  They  are 
originally  formed  and  lodged  within  the  cavity 
of  the  abdomen  ; and  it  is  not  till  after  the  child 
is  born,  or  very  near  that  time,  that  they  begin 
to  pafs  into  the  groin,  and  from  thence  into  the 
fcrotum  (m).  By  this  difpofition  they  are  very 
wifely  protected  from  the  injuries  to  which  they 
would  be  liable  to  be  expofed,  from  the  different 
pofitions  of  the  child  at  the  time  of  parturition. 

The  tefticles  in  this  ftate  are  loofely  attached 
to  the  pfose  mufcles,  by  means  of  the  peritonae- 
um by  which  they  are  covered  ; and  they  are  at 
this  time  of  life  connected  in  a very  particular 

T 2 manner 

(m)  It  fometimes  happens  in  difTefting  ruptures,  that  the 
intefUne  is  found  in  the  fame  fac,  and  in  contaft  with  the  teftis. 
This  appearance  was  at  firfl  attributed  to  a fuppofed  lacera- 
tion of  the  peritonseum  ; but  later  obfervations,  by  pointing 
out  the  fituationof  the  tefticles  in  the  foetus,  have  led  to  prove, 
that  the  teftis,  as  it  defcends  into  the  fcrotum,  carries  with 
it  a portion  or  elongation  of  the  peritonaeum,  which  becomes 
its  tunica  vaginalis,  or  a kind  of  fac,  in  which  the  tefticle  is 
lodged,  as  will  be  explained  in  the  courfe  of  this  feftion. 
The  communication  between  this  fac  and  the  cavity  of  the 
abdomen,  is  ufually  foon  cut  off ; but  in  fomefubjefts  it  con- 
tinues open  during  life  j|and  when  an  hernia  or  defcent  of  the 
inteftine  takes  place  in  a fuch  fubjeft,it  does  not  pulh  down 
a portion  of  the  peritonaeum  before  it,  as  it  muft  otherwife 
neceffarily  do,  but  paffes  at  once  through  this  opening,  and 
comes  in  contaft  with  the  naked  tefticle,  conftituting  that 
f articular  fpedes  of  rupture  called  hernia  congenita. 


292  OF  THE  ABDOMEN.  Part  III. 

manner  to  the  parietes  of  the  abdornen,  and  like- 
wife  to  the  fcrotiim,  by  means  of  a fubftance 
which  Mr.  Hunter  calls  the  ligament  ox guberna- 
culiim  teJUs^  becaufe  it  connedln  the  teftis  with 
the  fcrotiim,  and  diteds  its  courfe  in  its  defcent. 
This  gubernaculum  is  of  a pyramidal  form,  with 
its  bulbous  head  fixed  to  the  lower  end  of  the 
teftis  and  epididymis,  and  lofes  its  lower  and 
{lender  extremity  in  the  cellular  membrane  of  the 
fcrotum.  It  is  difficult  to  afcertain  what  the 
ftrudlure  and  compofition  of  this  gubernaculum 
is,  but  it  is  certainly  vafcular  and  fibrous  ; and* 
from  certain  circumftances*  it  would  feem  to  be 
in  part  compofed  of  the  cfemafter  mufcle,  run-  ! 
ning  upwards  to  join  the  lower  end  of  the  teftis. 

We  are  not  to  fuppofe  that  the  tefticle,  when 
defcended  into  the  fcrotum,  is  to  be  feen  loofe  as 
a piece  of  gut  or  omentum  would  be  in  a com- 
mon hernial  fac.  We  have  already  obfetved, 
that  during  its  refidence  in  the  cavity  of  the  ab- 
domen it  is  attached  to  the  peritonaeum,  which 
defcends  with  it ; fo  that  when  the  fac  is  com- 
pleted in  the  fcrotum,  the  tefticle  is  at  firft  at- 
tached only  to  the  pofterior  part  of  it,  while  the 
fore  part  of  it  lies  loofe,  and  for  fome  time 
fords  a communication  with  the  abdomen.  The 
fpermatic  chord,  which  is  made  up  of  the  fper- 
matic  artery  and  vein,  and  of  the  vas  deferens  or 
excretory  dudt  of  the  teftis,  is  clofely  attached 
behind  to  the  pofterior  part  of  this  elongation  of 
the  peritonaeum.  But  the  fore  part  of  the  peri-  1 

toneal  I 


Part  111.  OF  TOL  ABDOMEN.  293 

toneal  fac,  which  is  at  firft  loofe  and  not  attached 
to  the  tefticle,  clofes  after  a certain  time,  and  be- 
comes united  the  pofterior  part,  and  thus  per- 
fedily  furrounds  the  tefticle  as  it  were  in  a 
purfe. 

The  tefticles  of  the  foetus  differ  only  in  their 
fize  and  fituation  from  thofe  of  the  adult.  In 
their  paffage  from  the  abdomen  they  defeend 
through  the  abdominal  rings  into  the  ferotum, 
where  they  are  fupported  and  defended  by  vari- 
ous integuments. 

What  the  immediate  caufe  of  this  defeent  is, 
has  not  yet  been  fatisfaeftorily  determined.  It 
4 has  been  aferibed  to  the  effects  of  refpiration,  but 
the  tefticles  have  fometimes  been  found  in  the 
ferotum  before  the  child  has  breathed ; and  it 
does  not  feem  to  be  occafioned  by  the  aeftion  of 
the  cremafter  mufcle,  becaufe  the  fame  effefl 
would  be  liable  to  happen  to  the  hedge-hog,  and 
fome  other  quadrupeds,  w^hofe  tefticles  remain  in 
the  abdomen  during  life. 

The  ferotum,  v^^hieh  is  the  external  or  com- 
mon covering  of  both  tefticles,  is  a kind  of  fac 
formed  by  the  common  integuments,  and  exter- 
nally divided  into  two  equal  parts  by  a promi- 
nent line  called  raphe. 

In  the  inner  part  of  the  ferotum  we  meet  with 
a cellular  coat  called  dartos  (n),  which  by  its 

duplicature 

(n)  The  dartos  has  nfually  been  confidered  as  a mufcle, 
and  is  deferibed  as  fnch  both  by  Douglas  and  Winflow.  But 

there 


294  OF  THE  ABDOMEN.  Part  III. 
duplicature  divides  the  fcrotum  into  two  equal 
parts,  and  forms  what  is  called  feptum  fcroti, 
which  correfponds  with  the  raphe.  The  collap- 
fion  which  is  fo  often  obferved  to  take  place  in 
the  fcrotum  of  the  healthy  fubjedt,  when  excit- 
ed by  cold  or  by  the  ftimulus  of  venery,  feems 
to  be  very  properly  attributed  to  the  contrac- 
tile motion  of  the  fkin,  and  not  to  any  mufcular 
fibres,  as  is  the  cafe  in  dogs  and  fome  other  quad- 
rupeds. 

The  fcrotum,  then,  by  means  of  its  feptum, 
is  found  to  make  two  diftindl  bags,  in  which  the 
tefticles,  invefted  by  their  proper  tunics,  are  fe- 
cured  lodged  and  feparated  from  each  other,  j 
Thefe  coats  are  the  cremafter,  the  tunica  vagina- 
lis, and  the  tunica  albuginea.  The  ftrft  of  thefe 
is  compofed  of  mufcular  fibres,  and  is  to  be  con- 
fidered  only  as  a partial  covering  of  the  teftis ; 
for  it  furrounds  only  the  fpermatic  chord,  and 
terminates  upon  the  upper  and  external  parts  of 
the  tunica  vaginalis  teftis,  ferving  to  draw  up 
and  fufpend  the  tefticle  (o).  The  tunica  vaginalis 
teftis  has  already  been  defcribed  as  being  a thin 

production 

there  being  no  part  of  the  fcrotum  of  the  human  fubjeft 
■which  can  be  laid  to  confift  of  mufcular  fibres,  Albinus  and 
Haller  have  very  properly  omitted  to  defcribe  the  dartos  as 
a mufcle,  and  confider  it  merely  as  a cellular  coat. 

(o)  The  cremafter  mufcle  is  compofed  of  a few  fibres 
from  the  obliquus  internus  abdominis,  which  uniting  with  a 
few  from  the  tranfverfalis,  defcend  upon  the  fpermatic  chord, 
and  are  infenfibly  loft  upon  the  tunica  vaginalis  of  the  tefti- 
cle. It  ferves  to  fufpend  and  draw  up  the  tefticle. 


Part  III.  OF  THE  ABDOMEN.  295 

produdion  of  the  peritonaeum,  loofely  adhering 
every  where  to  the  tefticle,  which  it  includes  as 
it  were  in  a bag.  The  tunica  albuginea  is  a firm, 
white,  and  veiy  compadl:  membrane  of  a glif- 
tening  appearance,  which  immediately  invefts 
the  hody  of  the  teftis  and  the  epididymus  ; ferv- 
ing  in  fome  meafure  to  connedt  them  to  each 
other,  but  without  extending  itielf  at  all  to  the 
fpermatic  chord.  This  tunica  albuginea  ferves 
to  confine  the  growth  of  the  teftis  and  epididy- 
mus within  certain  limits,  and  by  giving  them 
a due  degree  of  firmnefs,  enables  them  to  per- 
form their  proper  fundfions. 

Having  removed  this  laft  tunic,  we  discover 
the  fubftance  of  the  tefticle  itfelf,  which  appears 
to  be  made  up  of  an  infinite  number  of  very 
elaftic  filaments,  which  may  be  beft  diftinguiih- 
ed  after  macerating  the  tefticle  in  v,nater.  Each 
tefticle  is  made  up  of  the  fpermatic  artery  and 
vein,  and  the  excretory  veffels  or  tubuli  femini- 
feri.  There  are  likewife  a great  number  of  ab- 
forbent  velfels,  and  fome  branches  of  nerves  to  be 
met  with  in  the  tefticles. 

The  fpermatic  arteries  arife  one  on  each  fide 
from  the  aorta,  generally  about  an  inch  below 
the  emulgents.  The  right  fpermatic  vein  com- 
monly pafles  into  the  vena  cava ; but  the  left 
fpermatic  vein  ufually  empties  itfelf  into  the 
emulgent  on  that  fide  ; and  it  is  fuppofed  to  take 
this  courfe  into  the  emulgent,  that  it  may  avoid 

paifing 


296  OF  THE  ABDOMEN.  Part  IIL 
palling  over  the  aorta,  which  it  would  be  oblig- 
ed to  do  in  its  way  to  the  vena  cava. 

The  blood  is  circulated  very  flowly  through 
the  fpermatic  artery,  which  makes  an  infinite 
number  of  circumvolutions  in  the  fubftance  of 
thetefticle,  where  it  depofitesthe  femen,  which 
palTes  through  the  tubuli  feminiferi.  Thefe  tu- 
buli  feminiferi  are  feen  running  in  ftiort  waves 
from  the  tunica  albuginea  to  the  axis  of  the  tefti- 
cle ; and  are  divided  into  diftinT  portions  by 
certain  thin  membranous  produdions,  which 
originate  from  the  tunica  albuginea.  They  at 
length  unite,  and  by  an  infinite  number  of  con- 
volutions form  a fort  of  appendix  to  the  teftis 
called  epididymis  (p),  which  is  a vafcular  body 
of  an  oblong  fhape,fituated  upon  the  fuperior  part 
of  each  tefticle.  Thefe  tubuli  of  the  epididymis 
at  length  form  an  excretory  dudf  called  vas  de- 
ferens^ which  afcends  towards  the  abdominal 
rings,  with  the  other  parts  that  make  up  the 
fpermatic  chord,  and  then  a feparation  takes 
places  the  neiA'^es  and  blood-veffels  palfing  on  to 
their  feveral  terminations,  and  the  vas  deferens 
going  to  depofit  its  femen  in  the  veficula!  femi- 
nales,  which  are  two  foft  bodies  of  a white  and 
convoluted  appearance  externally,  fituatcd  ob- 
liquely between  the  redlum  and  the  lower  part 

of 

(p)  The  tefticles  were  named  diclymi  by  the  ancients,  and 
the  name  of  this  part  was  given  to  it  on  account  of  its  fitua- 
tlon  upon  the  telUcle, 


Part  lil.  OF  THE  ABDOMEN.  297 

of  the  bladder,  and  uniting  together  at  the  lower 
extremity.  From  thefe  refervoirs  (q^),  which 

are 

(o^)  That  the  bags  called  veficiilx  femhmles  are  refervoirs 
of  femen,  is  a circumftance  which  has  been  by  anatomifts 
univerfally  believed.  Mr.  J.  Hunter,  however,  from  feveral 
circumflances,  has  been  induced  to  think  this  opinion  erro- 
neous. 

He  has  examined  thefe  veficulse  in  people  who  have  died 
fuddenly,  and  he  found  their  contents  to  be  different  in  their 
properties  from  the  femen.  In  thofe  who  had  loft  one  of 
the  tefticles,  or  the  ufe  of  one  of  them,  by  difeafe,  both  the 
veficulse  were  full,  and  their  contents  ftmilar.  And  in  a 
lufus  nature,  where  there  was  no  communication  between 
the  vafa  deferentia  and  veficulae,  nor  between  the  veficulae 
and  penis,  the  fame  thing  took  place. 

From  thefe  obfervations,  bethinks  we  have  a prefumptlv« 
proof.  That  the  femen  can  be  abforbed  in  the  body  of  the 
tefticle  and  in  the  epididymis,  and  that  the  veficulae  fecrete 
a mucus  which  they  are  capable  of  abforbing  when  it  cannot 
be  made  ufe  of : That  the  femen  is  not  retained  in  refervoirs 
after  it  is  lecreted,  and  kept  there  till  it  is  ufed  ; but  that  it 
is  fecreted  at  the  time,  in  confequcnce  of  certain  afteftions 
of  the  mind  ftimulating  the  tefticles  to  this  aflion. 

He  corroborates  his  obfervations  by  the  appearance  on 
diffeflion  in  other  animals  •,  and  here  he  finds.  That  the  fhape 
and  contents  of  the  veficulse  vary  much  in  different  animals, 
while  the  femen  in  moft  of  them  he  has  examined  is  nearly 
the  fame : That  the  vafa  deferentia  in  many  animals  do  not 
communicate  with  the  veficulse  : That  the  contents  of  the 
veficulse  of  caftrated  and  perfefl  animals  are  ftmilar,  and 
nearly  equal  in  quantity,  in  no  way  refembling  the  femen 
as  emitted  from  the  animal  in  coitu,  or  what  is  found  in  the 
vas  deferens  after  death.  He  obferves  likewilc,  that  the 
bulb  of  the  urethra  of  perfeft  males  is  conftderably  larger 
than  in  caftrated  animals. 

From  the  whole,  he  thinks  the  following  inferences  may 

be 


298  OF  THE  ABDOMEN.  Part  Ilf. 
are  plentifully  fupplied  with  blood-veffels  and 
nerves,  the  femen  is  occafionally  difcharged 
through  two  fhort  paflages,  which  open  into  the 

urethra 

be  fairly  drawn : That  the  bags  called  veficultz  feminales  are 
not  feminal  refervoirs,  but  glands  fecreting  a peculiar  mucus ; 
and  that  the  bulb  of  the  urethra  is  properly  fpeaking  the 
receptacle  of  the  femen,  in  which  it  is  accumulated  previous 
to  ejeftion. 

But  although  he  has  endeavoured  to  prove  that  the  vefi- 
culas  do  not  contain  the  femen,  he  has  not  been  able  to  af- 
certain  their  particular  ufe.  He  thinks,  however,  we  may 
be  allowed  upon  the  whole  to  conclude,  that  they  are,  toge- 
ther with  other  parts,  fubfervient  to  the  purpofes  of  gene-  1 
ration. 

Although  the  author  has  treated  this  fubjedf  very  ably, 
and  made  many  Ingenious  obfervations,  fome  things  may  be  ! 
objeffed  to  what  he  has  advanced  •,  of  which  the  following 
are  a few  : That  thofe  animals  who  have  bags  called  veficuhz 
fe7ninales  perform  copulation  quickly  5 whereas  others  that 
want  them,  as  in  the  dog  kind,  are  tedious  in  copulation : 
That  in  the  human  body,  at  leaft,  there  is  a free  communica- 
tion between  the  vafa  deferentia  and  veficulas ; and  in  ani- 
mals where  the  author  has  obferved  no  communication  be- 
tween the  vala  deferentia  and  veficulas,  there  may  be  a com- 
munication by  veffels  not  yet  difcovered,  and  which  may  be 
compared  to  the  hepato-cyftic  dufts  in  fowls  and  fifhes : — . 
That  the  fluid  in  the  end  of  the  vafa  deferentia  and  the  vefi-^1 
culfE  feminales  are  fimilar,  according  to  the  author’s  own  ob- J|[ 
fervation : That  the  veficuls  in  fome  animals  increafe  and 
decreafewith  the  tefticle  at  particular  feafons  : That  in  birds 
and  certain  fiflres,  there  is  a dilatation  of  the  ends  of  the  vafa„ 
deferentia,  which  the  author  himfelf  allows  to  be  a refer- 
voir  for  the  femen.  ^,^1 

AVith  refpedl  to  the  circumftance  of  the  bulb  of  the  u're-  „ 
thra  anfwering  the  purpofe  of  a refervoir,  the  author  has 
mention  no  fafts  which  tend  to  eftablifh  this  opinion.  Sec 
Obfervations  on  certain  Parts  of  the  Animal  Oeconomy^ 


Part  III.  OF  THE  ABDOMEN.  299 

urethra  clofe  to  a little  eminence  called  verumon^ 
taniim. 

Near  this  eminence  we  meet  with  the  prof- 
tate,  which  is  fituated  at  the  neck  of  the 
bladder,  and  is  defcribed  as  being  of  a glandu- 
lar ftrudfure.  It  is  fhaped  fomewhat  like  a heart 
with  its  fmall  end  foremoft,  and  inverts  the  ori- 
gin of  the  urethra.  Internally  it  appears  to  be 
of  a firm  fubrtance,  and  compofed  of  feveral  fol- 
licles, fecreting  a whitirti  vifcid  fluid,  that  is  dif- 
charged  by  ten  or  twelve  excretory  dudls  into 
the  urethra,  on  each  fide  of  the  openings  of  the 
veficulae  feminales  at  the  fame  time,  and  from  the 
fame  caufes  that  the  femen  is  expelled.  As  this 
latter  fluid  is  found  to  be  exceedingly  limpid  in 
the  veficulae  feminales  of  the  dead  fubjedt,  it 
probably  owes  its  whitenefs  and  vifcidity  to  this 
liquor  of  the  prortate. 

The  penis,  which  is  to  be  confidered  as  the 
vehicle  or  adfive  organ  of  procreation,  is  com- 
pofed of  two  columns,  the  corpora  cavernofa, 
corpus  fpongiofum.  The  corpora  cavernofa, 
which  conrtitute  the  greatert  part  of  the  penis, 
may  be  defcribed  as  two  cylindrical  ligamentous 
tubes,  each  of  which  is  compofed  of  an  infinite 
number  of  minute  cells  of  a fpongy  texture, 
which  communicate  with  each  other.  Thefe 
two  bodies  are  of  a very  pliant  texture,  and  ca- 
pable of  confiderable  diftenfion  : and  being  unit- 
ed laterally  to  each  other,  occafion  by  this  union 
a fpace  above  and  another  below.  The  upper- 

and 


300  OF  THE  ABDOMEN.  Part  III. 

moft  of  thefe  fpaces  is  filled  by  the  blood  veflels, 
and  the  lower  one,  which  is  larger  than  the  j 
other,  by  the  urethra  and  its  corpus  fpongiofum. 
Thefe  two  cavernous  bodies  are  at  firft  only  fe- 
parated  by  a partition  of  tendinous  fibres,  which  li 
allow  them  to  communicate  with  each  other ; but  t 
they  afterwards  divaricate  from  each  other  like 
the  branches  of  the  letter  Y,  and  diminifhing 
gradually  in  fize,  are  attached,  one  on  each  fidei,  ' 
by  means  of  the  ligamentum  fufpenforium  penis 
to  the  ramus  ifchii,  and  to  the  inferior  portion  of 
the  os  pubis. 

The  corpus  fpongiofum  penis,  or  corpus  fpon-  | 
giofum  urethi'se,  as  it  is  ftyled  by  fome  authors, 
begins  as  foon  as  the  urethra  has  paffed  the  prof- 
tate,  with  a thick  origin  almoft  like  a heart,  firft 
under  the  urethra,  and  afterwards  above  it,  be- 
coming gradually  thinner,  and  furrounding  the 
whole  canal  of  the  urethra,  till  it  terminates  in  a 
confiderable  expanfion,  and  conftitutes  what  is 
called  the  glans  penis ^ which  is  exceedingly  vaf- 
cular,  and  covered  with  papillse  like  the  tongue. 
The  cuticle  which  lines  the  inner  furface  of  || 
the  urethra,  is  continued  over  the  glans  in  the 
fame  manner  as  it  is  fpread  over  the  lips. 

The  penis  is  invefled  by  the  common  integu-  || 
ments,  but  the  cutis  is  refiefted  back  every  where 
from  the  glans  as  it  is  in  the  eye-lids  ; fo  that  it 
covers  this  part,  when  the  penis  is  in  a relaxed 
ftate,  as  it  were  with  a hood,  and  from  this  ufe  is  I 
called  prepuce. 


The 


Part  III.  OF  THE  ABDOMEN.  301 

The  prepuce  is  tied  down  to  the  under  part 
of  the  glans  by  a fmall  ligament  called  franum^ 
which  is  in  faO;  only  a continuation  of  the  cuticle 
and  cutis.  There  are  many  fimple  febaceous 
follicles  called  glandules  odorifera^  placed  round 
the  balls  of  the  glans  ; and  the  fluid  they  fecrete 
fen'^es  to  preferve  the  exquifite  fenfibility  of  this 
part  of  the  penis,  and  to  prevent  the  ill  effedts 
of  attrition  from  the  prepuce. 

The  urethra  may  be  deiined  to  be  a membran- 
ous canal,  paflTmg  from  the  bladder  through  the 
whole  extent  of  the  penis.  Several  very  frnail 
openings,  called  lacunee^  communicate  with  this 
canal,  trough  which  a mucus  is  difeharged  into 
it ; and  befides  thefe,  there  are  two  glands,  firft 
deferibed  by  Cowper,  as  fecreting  a fluid  for  lu- 
bricating the  urethra,  and  called  Copper  s glands 
(r)  ; and  Littre  * fpeaks  of  a gland  fituated- 
near  the  proftate,  as  being  deftined  for  the  fame 
ufe. 

The  urethra  being  continued  from  the  neck 
of  the  bladder,  is  to  be  confidered  as  making  part 
of  the  urinary  palTage  ; and  it  likewife  afibrds  a 
conveyance  to  the  femen,  which  we  have  obfen?^- 
ed  is  occalionally  difeh^ged  into  it  from  the  ve- 
ficulae  feminales.  The  dired;ion  of  this  canal 
being  firfl;  under  and  then  before  the  pubis,  oc~ 

cafions 

(r)  Both  Heifter  and  Morgagni  obferve,  that  they  have 
rometimes  not  been  able  to  find  thefe  glands  ; lb  that  they  do 
not  feem  to  exifi:  in  all  fubjefts. 

* Menioires  da  I'Acad.  Royak  des  Sciaiccsy  i "oo. 


302  OF  THE  ABDOMEN.  Part  III. 

cafions  a winding  in  its  courfe  from,  the  blad- 
der to  the  penis  not  unlike  the  turns  of  the  let- 
ter S. 

The  penis  has  three  pair  of  mufcles,  the  erec- 
tores,  acceleratores,  and  tranfverfales.  They 
pufh  the  blood  from  the  crura  to  the  fore  part  of 
the  corpora  cavernofa.  The  firft  originate  from 
the  tuberofity  of  the  ifchium,  and  terminate  in 
the  corpora  cavernofa.  The  acceleratores  arife 
from  the  fphinfter,  and  by  their  infertion  ferve 
to  comprefs  the  bulbous  part  of  the  urethra  ; 
and  the  tranfverfales  are  deftined  to  afford  a paf- 
fage  to  the  femen,  by  dilating  the  canal  of  the 
urethra. 

The  arteries  of  the  penis  are  chiefly  derived 
from  the  internal  iliacs.  Some  of  them  are  fup- 
pofed  to  terminate  by  pabulous  orifices  within 
the  corpora  cavernofa  and  corpus  fpongiofum  ; 
and  others  terminate  in  veins,  which  at  lafl  make 
up  the  vena  magna  dorfi  penis,  and  other  fmall- 
er  veins,  which  are  in  general  diflributed  in  like 
order  with  the  arteries. 

Its  nerves  are  large  and  numerous.  They 
arife  from  the  great  fciatic  nerve,  and  accom- 
pany the  arteries  in  their  courfe  through  the 
penis. 

We  have  now  defcribed  the  anatomy  of  this 
organ  ; and  there  only  remains  to  be  explained, 
how  it  is  enabled  to  att^lin  that  degree  of  firmnefs 
and  diflenfion  which  is  effential  to  the  great  work 
of  generation. 


0 


The 


Part  III.  OF  THE  ABDOMEN.  3(53 
The  greateft  part  of  the  penis  has  been  fpokeii 
of  as  being  of  a fpongy  and  cellular  texture, 
plentifully  fupplied  with  blood-veflels  and  nerves, 
and  as  having  mufcles  to  move  it  in  different  di- 
red;ions.  Now,  the  blood  is  conftantly  palling 
into  its  cells  through  the  fmall  branches  of  the 
arteries  which  which  open  into  them,  and  is 
from  thence  as  conftantly  returned  by  the  veins, 
fo  long  as  the  corpora  cavernofa  and  corpus  fpon- 
giofum  continue  to  be  in  a relaxed  and  pliant 
ftate.  But  when,  from  any  nervous  influence, 
or  other  means,  which  it  is  not  neceflfary  here 
I to  define  or  explain,  the  eredlores  penis,  ejacu- 
^ latores  feminis,  levatores  ani,  &c.  are  induced 
r to  contraft,  the  veins  undergo  a certain  degree 
( of  compreflion,  and  the  paffage  of  the  blood 
' through  them  is  fo  much  impeded,  that  it  col- 
! lefts  in  them  in  a greater  proportion  than  they 
' are  enabled  to  carry  off,  fo  that  the  penis  gradu- 
ally enlarges ; and  being  more  and  more  forcibly 
drawn  up  againft  the  os  pubis,  the  vena  magna 
itfelf  is  at  length  compreffed,  and  the  penis  be- 
comes fully  diftended.  But  as  the  caufes  which 
firft  occafioned  this  diftenfion  fubfide,  the  peni^ 
gradually  returns  to  its  ftate  of  relaxation. 

§ 2.  Female  Organs  of  Generation. 

Anatomical  writers  ufually  divide  the  fe- 
tnale  organs  of  generation  into  external  and  inter- 
nal. In  the  firft  divifion  they  include  the  mons 
^3  . veneris. 


304  OF  THE  ABDOMEN.  Part  HE* 

veneris^  Libia  pudendi^  perinaum^  clltvris^  nymph  ce^ 
and  carunculix  myrtiformes ; and  in  the  latter,  the 
vagina-,  with  the  ntsrm  and  its  appendages.  ^ 

The  mans  veneris^  which  is  placed  on  the  upper  j 
part  of  the  fymphyfis  pubis,  is  internally  com- 
pofed  of  adipofe  membranes,  which  makes  it  * 
i'oft  and  prominent : it  divides  into  two  parts 
called  labia  pudendi^  which  defcending  towards 
the  redtum,  from  which  they  are  divided  by  the 
perinasum,  form  what  is  called  the  jhurckttte^  | 
The  perinaeum  is  that  flefhy  fpace  which  extends  i 
about  an  inch  and  an  half  from  the  fourchette  to 
the  anus,  and  from  thence  about  two  inches  to 
the  coccyx. 

The  labia  pudendi  being  feparated,  we  obferve^ 
a fulcus  called  fo^a  magni ; in  the  upper  part  of  vjl 
which  is  placed  the  clitoris,  a fmall  round  fpongy 
body,  in  fome  meafure  refembling  the  male  pe- 
nis, but  impervious,  compofed  of  two  corpora 
cavernofa,  arifmg  from  the  tuberofities  of  the  ‘ 
oha  iichii ; fiirnifhed  with  two  pair  of  mufcles,  | 
the  eredtores  clitoridis,  and  the  fphin£ter  or  con- 
ftri(Tor  oftii  vaginse  ; and  terminating  in  a glans, 
which  is  covered  with  its  prepuce.  From  the 
lower  part,  on  each  fide  of  the  folia,  pafs  the 
nymphse,  tvs^o  membranous  and  fpongy  folds 
which  feem  deftined  for  ufcful  purpofes  in  partu- 
rition, by  tending  to  enlarge  the  volume  of  the 
vagina  as  the  child’s  head  paffes  through  it.  Be- 
tween thefe,  about  the  middle  of  the  foffa  mag- 
na,  -WQ  perceive  the  orifice  of  the  vagina  or  os  ex- 
2 ternum, 


Part  III.  OF  THE  ABDOMEN.  305 

ternum,  clofed  by  folds  and  wrinkles  ; and  about 
^ half  an  inch  above  this,  and  about  an  inch  be- 
/ low  the  clitoris,  appears  the  meatus  urinarius  or 
i orifice  of  the  urethra,  much  fhorter,  though 
fomewhat  larger,  than  in  men,  with  a little  pro- 
minence at  its  lower  edge,  which  facilitates  the 
introduction  of  the  catheter. 

The  os  externum  is  furrounded  internally  by 
J feveral  membranous  folds  called  caruticulce  myr~ 
' tiformes^  which  are  partly  the  remains  of  a thin 
^ membrane  called  hymen ^ that  covers  the  vagina 
in  children.  In  general  the  hymen  is  fufficiently 
*iOpen  to  admit  the  paffage  of  the  menfes,  if 
i it  exifts  at  the  time  of  their  appearance  ; fome- 
j times,  however,  it  has  been  found  perfectly 
clofed. 

' The  vagina,  fituated  between  the  urethra  and 
the  reCtum,  is  a membranous  cavity,  furround- 
led  efpecially  at  its  external  extremity  with  a 
fpongy  and  vafcular  fubftance,  which  is  covered 
by  the  fphinCter  oftii  vaginae.  It  terminates  in 
the  uterus,  about  half  an  inch  above  the  os  tin- 
, cae,  and  is  wider  and  fliorter  in  women  who 
^ have  had  children  than  in  virgins. 

» All  thefe  parts  are  plentifully  fupplied  with 
H blood-veflels  and  nerves.  Around  the  nymphse 
I there  are  febaceous  follicles,  which  pour  out  a 
f fluid  to  lubricate  the  inner  furface  of  the  vagina  ; 
l and  the  meatus  urinarius,  like  the  urethra  in  the 
' male  fubjeCt,  is  conftantly  raoiftened  by  a mu- 

U cus, 


3o5  of  the  ABDOMEJT.  Part  III. 

cus,  which,  defends  it  againft  the  acrimony  of 
the  urine. 

The  uterus  is  a hollow  vifcus,  fituated  in  the 
hypogaftric  region,  between  the  redtum  and  blad- 
der. It  is  deftined  to  receive  the  firft  rudiments 
of  the  foetus,  and  to  alTift  in  the  developement 
of  all  its  parts,  till  it  arrives  at  a ftate  of  per- 
feftion,  and  is  fitted  to  enter  into  the  world, 
at  the  time  appointed  by  the  wife  Author  of 
nature. 

The  uterus,  in  its  unimpregnated  ftate,  refem- 
bles  a pear  in  fhape,  fomewhat  flattened,  with 
its  fundus  or  bottom  part  turned  towards  the  ab- 
domen, and  its  cervix  or  neck  furrounded  by  the 
vagina.  The  entrance  into  its  cavity  forms  a 
little  protuberance,  which  has  been  compared  to 
the  mouth  of  a tench,  and  is  therefore  called  os 
titiccs. 

The  fubftance  of  the  uterus,  which  is  of  a 
confiderable  thicknefs,  appears  to  be  compofed 
of  mufcular  and  fmall  ligamentous  fibres,  fmall 
branches  of  nerves,  fortie  lymphatics,  and  with  II 
arteries  and  veins  innumerable.  Its  nerves  are 
chiefly  derived  from  the  intercoftal,  and  its  arte- 
ries and  veins  from  the  hypogaftric  and  fpermatic. 
The  membrane  which  lines  its  cervix,  is  a con- 
tinuation of  the  inner  membrane  of  the  vagina ; 
but  the  outer  furface  of  the  body  of  the  uterus 
is  covered  with  the  peritonaeum,  which  is  re- 
fle<fted  over  it,  and  defcends  from  thence  to  the 
inteftinum  recftum.  This  duplicature  of  the 

peritonaeum, 


Part  III.  OF  THE  ABDOMEN.  307 

peritonseum,  by  paffirig  off  from  the  fides  of 
the  uterus  to  the  ftdes  of  the  pelvis,  is  there 
firmly  connedted,  and  forms  what  are  called 
ligamenta  uteri  lata ; which  not  only  ferve  to 
fupport  the  uterus,  but  to  convey  nerves  and 
blood- vefTels  to  it. 

The  ligamenta  uteri  rotunda  arife  from  the 
Tides  of  the  fundus  uteri,  and  paffing  along  with- 
in the  fore-part  of  the  ligamenta  lata,  defcend 
through  the  abdominal  rings,  and  terminate  in 
the  fubftance  of  the  mens  veneris.  The  fiib- 
ftance  of  thefe  ligaments  is  vafcular,  and  al- 
though both  they  and  the  ligamenta  lata  admit 
the  uterus  in  the  virgin  ftate,  to  move  only  about 
I an  inch  up  and  down,  yet  in  the  courfe  of  preg- 
i nancy  they  admit  of  confiderable  diftenfion,  and 
j after  parturition  return  nearly  to  their  original 
ftate  with  furprifing  quicknefs. 

! On  each  fide  of  the  inner  furface  of  the  ute- 
rus, in  the  angle  near  the  fundus,  a fmall  orilice 
is  to  be  difeovered,  which  is  the  beginning  of 
one  of  the  tubse  fallopian^.  Each  of  thefe  tubes, 
which  are  two  in  number,  paffing  through  the 
fubftance  of  the  uterus,  is  extended  along  the 
broad  ligaments-,  till  it  reaches  the  edge  of  the 
pelvis,  from  whence  it  refiedts  back  ; and  turn- 
ing over  behind  the  ligaments,  about  an  inch  of 
its  extremity  is  feen  hanging  loofe  in  the  pelvis, 
near  the  ovarium.  Thefe  extremities,  having 
a jagged  appearance,  are  called  fimhrice^  or  morfus 
dlaboli.  Each  tuba  Fallopiana  is  ufually  about 

U 2 three 


'o8  OF  THE  ABDOMEN.  , Part  IIL 
three  or  four  inches  long.  Their  cavities  are 
at  firft  very  fmall,  but  become  gradually  larger, 
like  a trumpet,  as  they  approach  the  fimbriae. 

Near  the  fimbriae  of  each  tuba  Fallopiana, 
about  an  inch  from  the  uterus,  is  fituated  an  oval 
body  called  ovarium^  of  about  half  the  fize  of 
the  male  tefticle.  Each  of  thefe  ovaria  is  cover- 
ed by  a production  of  the  peritonaeum,  and 
hangs  loofe  in  the  pehis.  They  are  of  a flat 
and  angular  form,  and  appear  to  be  compofed 
of  a white  and  cellular  fubftance,  in  which  we 
are  able  to  difcover  feveral  minute  veficles  filled 
with  a coagulable  lymph,  of  an  uncertain  num- 
ber, commonly  exceeding  1 2 in  each  ovary.  In 
the  female  of  riper  years,  thefe  veficles  become 
exceedingly  turgid,  and  a kind  of  yellow  coa- 
gulum  is  gradually  formed  within  one  of  them, 
which  increafes  for  a certain  time.  In  concep- 
tion, one  of  thefe  mature  ova  is  fuppofed  to  be 
impregnated  with  the  male  femen,  and  to  be 
fqueezed  out  of  its  nidus  into  the  Fallopian 
tube  ; after  which  the  ruptured  part  forms  a 
fubftance  which  in  fome  animals  is  of  a yel- 
low colour,  and  is  therefore  called  corpus  lute- 
um ; and  it  is  obfervable,  that  the  number  of 
thefe  fears  or  filTures  in  the  ovarium,  conftantly 
correfponds  with  the  number  of  foetufes  exclud- 
ed by  the  mother. 


§3-  Of 


Part  III. 


OF  THE  ABDOMEN. 


3'^9 

§ 3.  Of  Conception. 

Man,  being  ever  curious  and  inquifitive, has 
naturally  been  led  to  enquire  after  the  origin  of 
his  exiftence  ; and  the  fubjedl  of  generation  has 
employed  the  philofophical  world  in  all  ages  : 
but  in  following  nature  up  to  her  minute  re- 
cefles,  the  philofopher  foon  finds  himfelf  bewil- 
dered, and  his  imagination  often  fupples  that 
which  he  fo  eagerly  wifhes  to  difcover,  but  which 
is  deftined  perhaps  never  to  be  revealed  to  him. 
Of  the  many  theories  which  have  been  formed 
on  this  fubjeft,  that  of  the  ancient  philofophers 
feems  to  have  been  the  moll  fimple  ; they  con- 
fidered  the  male  femen  as  alone  capable  of  form- 
ing the  foetus,  and  believed  that  the  female  only 
afforded  it  a lodging  in  the  womb,  and  fuppiied 
it  with  a nourilhment  after  it  was  perfeftly  form- 
ed. This  opinion,  however,  foon  gave  place  to 
another,  in  which  the  female  was  allowed  a more 
confiderable  fhare  in  conception. 

This  fecond  fyftem  confidered  the  foetus  as 
being  formed  by  the  mixture  of  the  feminal  li- 
quor of  both  fexes,  by  a certain  arrangement  of 
its  feveral  particles  in  the  uterus.  But  in  the 
1 6th  century,  veficles  or  eggs  were  difcovered 
in  the  ovaria  or  female  tefticles  ; the  foetus  had 
been  found  fometimes  in  the  abdomen,  and 
fometimes  in  the  Fallopian  tubes  ; and  the  two 
former  opinions  were  exploded  in  favour  of  a 

nev7 


210 


OF  THE  ABDOMEN.  Part  III. 
new  do(Triiie.  The  ovaria  were  compared  to  a 
bunch  of  grapes,  being  fuppofed  to  confift  of  ve- 
ficles,  each  of  which  had  a ftalk  ; fo  that  it  might 
be  difengaged  without  hurting  the  reft,  or  fpill- 
ing  the  liquor  it  contained.  Each  veficle  was 
faid  to  include  a little  animal,  almoft  complete 
in  all  its  parts  ; and  the  vapour  of  the  male  fe- 
men  being  conveyed  to  the  ovarium,  was  fup- 
pofed to  produce  a fermentation  in  the  veficle, 
which  approached  the  neareft  to  maturity  ; and 
inducing  it  to  difengage  itfelf  from  the  ovarium, 
it  paffed  into  the  tuba  Fallopiana,  through 
which  it  was  conveyed  to  the  uterus.  Here  it 
was  fuppofed  to  take  root  like  a vegetable  feed, 
and  to  form,  with  the  veffels  originating  from 
the  uterus,  what  is  called  placenta  ; by  means 
of  which  the  circulation  is  carried  on  between 
the  mother  and  the  foetus. 

This  opinion,  with  all  its  abfurdities,  conti- 
nued to  be  almoft  univerfally  adopted  till  the 
clofe  of  the  fame  century,  when  Lieuwenhoeck, 
by  means  of  his  glaffes,  difeovered  certain 
opake  particles,  which  he  deferibed  as  fo  many 
animalcula,  floating  in  the  feminal  fluid  of  the 
male. 

This  difeovery  introduced  a new  fchifm  among 
the  philofophers  of  that  time,  and  gave  rife  to 
a fyftcm  vv'hich  is  not  yet  entirely  exploded. 
According  to  this  theory  the  male  femen  palling 
into  the  tubas'  Fallopianse,  one  of  the  animalcula 
penetrates  into  the  fubftance  of  the  ovarium, 

and 


21  I 


Part  III.  OF  THE  ABDOMEN, 
and  enters  into  one  of  its  veficles  or  ova.  This 
impregnated  ovum  is  then  fqueezed  from  its 
hulk,  through  the  coats  of  the  ovarium,  and  be- 
ing feized  by  the  fimbriae,  is  conduced  through 
the  tube  to  the  uterus,  -where  it  is  nourifhed  till 
it  arrives  at  a ftate  of  perfection.  In  this  fyf- 
tem  there  is  much  ingenuity  ; but  there  are  cer- 
tain circumftances  fuppofed  to  take  place,  which 
have  been  hitherto  inexplicable.  A celebrated 
modern  writer,  M.  Buffon,  endeavours  to  re- 
ftore,  in  fome  meafure,  the  moft  ancient  opi- 
nion, by  allowing  the  female  femen  a fhare  in 
this  office  ; aflerting,  that  animalcula  or  organic 
particles  are  to  be  difcovered  in  the  feminal  li- 
quor of  both  fexes  : he  derives  the  female  femen 
from  the  ovaria,  and  he  contends  that  no  ovum 
exifts  in  thofe  parts.  But  in  this  idea  he  is  evi- 
dently miftaken  ; and  the  opinion  now  moft  ge- 
nerally adopted  is,  that  an  impregnation  of  the 
ovum,  by  the  influence  of  the  male  femen,  is 
elTential  to  conception  (s).  That  the  ovum  is  to 
be  impregnated,  there  can  be  no  doubt ; but  as 
the  manner  in  which  fuch  an  impregnation  is 
fuppofed  to  take  place,  and  the  means  by  which 
the  ovum  afterwards  get  into  the  Fallopian  tube, 

and 

(s)  The  learned  Abbe  Spallanzani  has  thrown  much  light 
on  this  curious  lubjedt,  and  has  proved  by  a variety  of  ex- 
periments than  the  animalcule  exifts  entire  inthefemale  ovum, 
and  that  the  male  feed  is  only  neceftary  to  vivily  and  put  it 
in  motion. — His  experiments  and  obfervations  are  worthy 
of  the  attentive  perufal  of  every  phyfiologift. 


212 


OF  THE  ABDOMEN.  Part  HI. 
and  from  thence  into  the  uterus,  are  ftill  found- 
ed chiefly  on  hypothefis,  we  will  not  attempt  to 
extend  farther  the  inveftigation  of  a fubjedl;  con- 
cerning which  fo  little  can  be  advanced  with  cer- 
tainty. 

§ 4.  Of  the  Foetus  in  Utero. 

Opportunities  of  diffediing  the  human 
gravid  uterus  occurring  but  feldom,  the  ftate  of 
the  embryo  (t)  immediately  after  conception 
cannot  be  perfectly  known. 

When  the  ovum  defcends  into  the  uterus,  it 
is  fuppofed  to  be  very  minute  ; and  it  is  not  till 
a confiderable  time  after  conception  that  the 
rudiments  of  the  embryo  begin  to  be  afcer- 
tained. 

About  the  third  or  fourth  week  the  eye  may 
difcover  the  firft  lineaments  of  the  foetus ; but 
thefe  lineaments  are  as  yet  very  imperfect,  it  be- 
ing only  about  the  fize  of  a houfe-fly.  Two 
little  velTels  appear  in  an  almofl;  tranfparent  jel- 
ly ; the  largeft  of  which  is  deftined  to  become 
the  head  of  the  foetus,  and  the  other  fmaller  one 
is  referved  for  the  trunk.  But  at  this  period  no 
extremities  are  to  be  feen ; the  umbilical  cord 
appears  only  as  a very  minute  thread,  and  the 

placenta 

(t)  The  rudiments  of  the  child  are  ufnally  diftingihfhed  by 
this  name  till  the  human  figure  can  be  diftinftly  alcertained, 
and  then  it  has  the  appellation  of faeius. 


Part  III.  OF  THE  ABDOMEN.  213 
placenta  does  not  yet  abforb  the  red  particles  of 
the  blood.  At' fix  weeks,  not  only  the  head  but 
the  features  of  the  face  begin  to  be  developed. 
The  nofe  appears  like  a fmall  prominent  line, 
and  we  are  able  to  difcover  another  line  under  it, 
which  is  deftined  for  the  feparation  of  the  lips. 
Two  black  points  appear  in  the  place  of  eyes, 
and  two  minute  holes  mark  the  ears.  At  the 
fides  of  the  trunk,  both  above  and  below,  we 
fee  four  minute  protuberances,  which  are  the 
the  rudiments  of  the  arms  and  legs.  At  the  end 
of  eight  weeks  the  body  of  the  foetus  is  upwards 
of  an  inch  in  length,  and  both  the  hands  and 
feet  are  to  be  diftinguilhed.  The  upper  extre- 
mities are  found  to  increafe  fafter  than  the  lower 
ones,  and  the  feparation  of  the  fingers  is  accom- 
plifhed  fooner  than  that  of  the  toes. 

At  this  period  the  human  form  may  be  deci- 
fively  afceitained  ; — all  the  parts  of  the  face  may 
be  diftinguilhed,  the  fliape  of  the  body  is  clearly 
marked  out,  the  haunches  and  the  abdomen  are 
elevated,  the  fingers  and  toes  are  feparated  from 
each  other,  and  the  inteftines  appear  like  minute 
threads. 

At  the  end  of  the  third  month,  the  foetus  mea- 
fures  about  three  inches  ; at  the  end  of  thd  fourth 
month,  five  inches  ; in  the  fifth  month,  fix  or 
feven  inches ; in  the  fixth  month,  eight  or  nine 
inches  ; in  the  feventh  month,  eleven  or  twelve 
inches  ; in  the  eighth  month,  fourteen  or  fif- 
teen inches  ; and  at  the  end  of  the  ninth  month. 


or 


214  OF  THE  ABDOMEN.  Part  HI. 
or  full  time,  from  eighteen  to  twenty-two  in- 
ches. But  as  we  have  not  an  opportunity  of  ex- 
amining the  fame  fetus  at  different  periods  of 
pregnancy,  and  as  their  fize  and  length  may  be 
influenced  by  the  conftitution  and  mode  of  life- 
of  the  mother,  calculations  of  this  kind  muft  be 
very  uncertain. 

The  fetus  during  all  this  time  affumes  an  dval 
figure,  which  correfponds  with  the  fhape  of  the 
uterus.  Its  chin  is  found  reclining  on  its  breafl 
with  its  knees  drawn  up  towards  its  chin,  and  its 
arms  folded  over  them.  But  it  feems  likely, 
that  the  pofture  of  fome  of  thefe  parts  is  varied 
in  the  latter  months  of  pregnancy,  fo  as  to  caufe 
thofe  painful  twitches  which  its  mother  ufually 
feels  from  time  to  time.  In  natural  cafes,  its' 
head  is  probably  placed  towards  the  os  tinc;^  from 
the  time  of  conception  to  that  of  its  birth ; 
though  formerly  it  was  confidered  as  being  plac- 
ed towards  the  fundis  uteri  till  about  the  eighth 
or  ninth  mouth,  when  the  head,  by  becom- 
ing fpecifically  heavier  than  the  other  parts 
of  the  body,  was  fuppofed  to  be  turned  down- 
wards. 

The  capacity  of  the  uterus  increafes  in  pro- 
portion to  the  growth  of  the  fetus,  but  without 
becoming  thinner  in  its  fuhflance,  as  might  na- 
turally be  expeded.  The  nourifliment  of  the 
fetus,  during  all  this  time,  feems  to  be  derived 
from  the  placenta,  which  appears  to  be  original- 
ly formed  by  that  part  of  the  ovum  which  is 

next 


Part  HI.  OF  THE  ABDOMEN.  215 

next  the  fundis  uteri.  The  remamg  part  of  the 
ovum  is  covered  by  a membrane  called  fpongy 
chorion  {u)  ; within  which  is  another  called  true 
chorion^  which  includes  a third  termed  mnnios  (v): 
this  contains  a watery  fluid,  which  is  the  liquor 
amnii  (w),  in  which  the  foetus  floats  till  the 
time  of  its  birth.  On  the  fide  next  the  foetus,  the 
placenta  is  covered  by  the  amnios  and  true  cho- 
rion ; on  the  fide  next  the  mother  it  has  a pro- 
duction continued  from  the  fpongy  chorion. 

The 

(u)  Dr.  Hunter  has  defcribed  this  as  a lamella  from  the 
inner  furface  of  the  uterus.  In  the  latter  months  of  preg- 
nancy it  becomes  gradually  thinner  and  more  connefled  with 
the  chorion  : he  has  named  it  membrana  caduca,  or  decidua^ 
as  it  is  call  off  with  the  placenta.  Signior  Scarpa,  with 
more  probability,  confiders  it  as  being  compofed  of  an  in- 
fpifiated  co.igulable  lymph. 

(v)  In  fome  quadrupeds,  the  urine  appears  to  be  con- 
veyed from  the  bladder  through  a canal  called  urachus,  to 
the  allantois,  which  is  a refervoir,  refembling  a large  and 
blind  gut,  fituated  between  the  chorion  and  amnios.  The 
human  foetus  feems  to  have  no  fuch  refervoir,  though  fome 
writers  have  fuppofedthat  it  doesexift.  From  the  top  of  the 
bladder  afew  longitudinal  fibres  are  extended  to  the  umbilical 
chord  ; and  thefe  fibres  have  been  confidered  as  the  urachus, 
though  without  having  been  ever  found  pervious. 

(w)  The  liquor  amnii  coagulates  like  the  lymph.  It  has 
been  fuppofed  to  pafs  into  the  osfophagus,  and  to  afford  nou- 
rifliment  to  the  foetus  ; but  this  does  not  feem  probable. 
Children  have  come  into  the  world  without  an  oefophagus, 
or  any  communication  between  the  ftomach  and  the  mouth  ; 
but  there  has  been  no  well  attefled  inftance  of  a child’s  hav- 
ing been  born  without  a placenta;  and  it  does  not  feem  like- 
ly, that  any  of  the  fluid  can  be  abforbed  through  the  pores 
of  the  fkin,  the  Ikin  in  the  foetus  being  every  where  covered 
with  a great  quantity  of  mucus. 


2i6  of  the  abdomen.  Part  III. 

The  amnios  and  chorion  are  remarkably  thin  and 
tranfparent,  having  no  blood-veflels  entering  in- 
to their  compofition.  The  fpongy  chorion  is 
opake  and  vafcular. 

In  the  firft  months  of  pregnancy,  the  involu- 
cra  bear  a large  proportion  to  their  contents  ; but 
this  proportion  is  afterwards  reverfed,  as  the  foe- 
tus increafes  in  bulk. 

The  placenta,  which  is  the  medium  through 
which  the  blood  is  conveyed  from  the  mother 
to  the  foetus,  and  the  manner  in  which  this 
conveyance  takes  place,  deferve  next  to  be  con- 
iidered. 

The  placenta  is  a broad,  flat,  and  fpongy  fub- 
ftance,  like  a cake,  clofely  adhering  to  the  inner 
furface  of  the  womb,  ufually  near  the  fundus, 
and  appearing  to  be  chiefly  made  up  of  the  rami- 
fications of  the  umbilical  arteries  and  vein,  and 
partly  of  the  extremities  of  the  uterine  veflels. 
The  arteries  of  the  uterus  difcharge  their  con- 
tents into  the  fubftance  of  this  cake  ; and  the 
veins  of  the  placenta,  receiving  the  blood  either 
by  a diredt  communication  of  veffels,  or  by  ab- 
forption,  at  length  form  the  umbilical  vein, 
which  paffes  on  to  the  finus  of  the  vena  porta, 
and  from  thence  to  the  vena  cava,  by  means  of 
the  canalis  venofus,  a communication  that  is 
clofed  in  the  adult.  But  the  circulation  of  the 
blood  through  the  heart  is  not  conducted  in  the 
foetus  as  in  the  adult : in  the  latter  the  blood  is 
carriedfrom  the  right  auricle  of  the  heart  through 

the 


Part  III.  OF  THE  ABDOMEN.  217 
the  pulmonary  artery,  and  is  returned  to  the  left 
auricle  by  the  pulmonary  vein  ; but  a dilatation 
of  the  lungs  is  eflential  to  the  paflage  of  the 
blood  through  the  pulmonary  veflels,  and  this 
dilatation  cannot  take  place  till  after  the  child  is 
bom  and  has  refpired.  This  deficiency,  howe- 
ver, is  fupplied  in  the  foetus  by  the  immediate 
communication  between  the  right  and  left  auri- 
cle, through  an  oval  opening,  in  the  feptum 
which  divides  the  two  auricles,  called  foramen 
ovale.  The  blood  is  likewife  tranfmitted  from 
the  pulmonary  artery  to  the  aorta,  by  means  of 
a du(ft  called  canalis  arteriofus^  which,  like  the. 
canalis  venofus,  and  foramen  ovale,  gradually 
clofes  after  birth. 

The  blood  is  returned  again  from  the  foetus 
through  two  arteries  called  the  umbilical  arteries^ 
which  arife  from  the  iliacs.  Thefe  two  veflels 
taking  a winding  courfe  with  the  vein,  form 
with  that,  and  the  membranes  by  which  they 
are  furrounded,  what  is  called  the  umbilical  chord. 
Thefe  arteries,  after  ramifying  through  the  fub- 
ftance  of  the  placenta,  difcharge  their  blood  into 
the  veins  of  the  uterus  ; in  the  fame  manner  as 
the  uterine  arteries  difcharged  their  blood  into 
the  branches  of  the  umbilical  vein.  So  that  the 
blood  is  conftantly  paffing  in  at  one  fide  of  the 
placenta  and  out  at  the  other ; but  in  what  par- 
ticular manner  it  gets  through  the  placenta  is  a 
point  not  yet  determined. 


EXPLA- 


OE  THE  ABDOMEN.  Part  III. 


2tB 

EXPLANATION  of  Plates  XXV.  XXVL  and  XXVII. 
Plate  XXV. 

Fig.  1.  Shows  the  Contents  of  the  Thorax  and 
Abdomen  in  fitu. 

I.  Top  of  the  trachea,  or  wind-pipe.  22, 
The  internal  jugular  veins.  3 3,  The  fubcla- 
vian  veins.  4,  The  vena  cava  defcendens.  5, 
The  right  auricle  of  the  heart.  6,  The  right 
ventricle.  7,  Part  of  the  left  ventricle.  8,  The 
aorta  defcendens.  9,  The  pulmonary  artery. 
I o,  The  right  lung,  part  of  which  is  cut  off  to 
fhow  the  great  blood-veifels.  1 1 , The  left  lung, 
entire.  1212,  The  anterior  edge  of  the  dia- 
phragm. 1 3 1 3)  The  two  great  lobes  of  the 
liver.  14,  The  ligamentum  rotundum.  15, 
The  gall-bladder.  16,  The  ftomach.  17  I7> 
The  jejunum  and  ilium.  1 8,  The  fpleen. 

Fig.  2.  Shows  the  Organs  fubfervient  to  the 
Chylopoietic  Vifcera, — ^with  thofe  of  the  U- 
rine  and  Generation. 

I I , The  under  fide  of  the  two  great  lobes 
of  the  liver,  a,  Lobulus  Spigelii.  2,  The  li- 
gamentum rotundum.  3,  The  gall-bladder. 
4,  The  pancreas,  5,  The  fpleen.  6 6,  The 
kidneys.  7,  The  aorta  defcendens.  8,  Vena 

cava 


? Part  III.  OF  THE  ABDOMEN.  31^ 
cava  afcendens.  9 9,  The  renal  veins  covering 
the  arteries,  i o,  A probe  under  the  fpermatic 
veflels  and  a bit  of  the  inferior  mefenteric  artery, 
and  over  the  ureters.  1 1 1 1 , The  ureters. 
12  12,  The  iliac  arteries  and  veins.  1 3,  The 
redtum  inteftinum.  14,  The  bladder  of  urine. 

Fio.  3.  Shows  the  Chylopoietic  Vifcera,  and 
Organs  fubfervient  to  them,  taken  out  of  the 
Body  entire. 

A[A  the  under  fide  of  the  two  great  lobes  of 
I the  liver.  B,  Ligamentum  rotundum.  C,  The 
gall-bladder.  D,  Dudfus  cyfticus.  E,  Dudius 
hepaticus.  F,  Dudiis  communis  choledochus. 
•G,  Venaportarum.  H,  Arteria  hepatica.  II, 
The  ftomach.  K K,  Venae  & arteriae  gaftro- 
epiploicse,  dextrse  & fmiftrs.  L L,  Venae  & 
arteriae  coronariae  ventriculi.  M,  The  fpleen, 
N N,  Mefocolon,  with  its  veflels.  O O O,  In- 
teftinum colon.  P,  One  of  the  ligaments  of 
the  colon,  which  is  a bundle  of  longitudinal 
'mufcular  fibres.  Jejunum  and 

ilium.  R R,  Sigmoid  flexure  of  the  colon  with 
the  ligament  continued,  and  over  S,  The  rec- 
tum inteftinum.  T T,  Levatores  ani.  U, 
Sphindfer  ani.  V,  The  place  to  which  the  pro^ 
ftate  glandis  canne<fted.  W,  The  anus. 


Fig.  4. 


320  OF  THE  ABDOMEN,  Part  III. 
Fig  4.  Shows  the  heart  of  a Foetus  at  the  full 
time,  with  the  Right  Auricle  cut  open  to 
fhow  the  Foramen  Ovale,  or  paffage  between 
both  Auricles. 

a.  The  right  ventricle,  b.  The  left  ventricle, 
c c.  The  outer  fide  of  the  right  auricle  ftretched 
out.  d d,  The  pofterior  fide,  which  forms  the 
anterior  fide  of  the  feptum.  e.  The  foramen 
ovale,  which  the  membrane  or  valve  which  co- 
vers the  left  fide,  f.  Vena  cava  inferior  paffing 
through  g,  A portion  of  the  diaphragm. 

Fig.  5*.  Shows  the  Heart  and  Large  Veffels  of  a 
Foetus  at  the  full  time. 

a.  The  left  ventricle,  b.  The  right  ventri- 
cle. c,  A part  of  the  right  auricle,  d.  Left 
auricle,  ee.  The  right  branch  of  the  pulmona- 
ry artery,  f,  Arteria  pulmonalis.  g g.  The 
left  branch  of  the  pulmonary  artery,  with  a num- 
ber of  its  largeft  branches  dilTedied  from  the 
lungs,  h.  The  canalis  arteriofus.  i.  The  arch 
of  the  aorta,  kk.  The  aorta  defcendens.  1,  The 
left  fubclavian  artery,  m.  The  left  carotid  ar- 
tery. n.  The  right  carotid  artery,  o.  The 
right  fubclavian  artery,  p.  The  origin  of  the 
right  carotid  and  right  fubclavian  arteries  in  one 
common  trunk,  q.  The  vena  cava  fuperior  or 
defcendens.  r.  The  right  common  fubclavian 
vein,  s.  The  left  common  fubclavian  vein. 

N.  B.  All  the  parts  defcribed  in  this  figure 
are  to  be  found  in  the  adult,  except  the  canalis 
arteriofus.  Plate 


Ax  AT  OXLY 


PlateXXY 


331 


Part.  Ill  OF  TfJE  ABCOteN. 


Plate  XXVL 

Fig.-  I.  Exhibits  the  more  fuperficial  Lympha- 
tie  Veflek  of  the  Lower  Extremity. 

Ay  The  fpine  of  the  os  ilium.  B,  The  es 
t pubis.  G,  The  iliac  artery.  D,  The  knee,  E E Fj 
I Branches  of  the  crural  artery.-  Gy  The  mufcu- 
I lus  ga-ftrocnemius.  H,  The  tibia.  I,  The  teh- 
\ don  of  the  mufculu's  tibialis  antieus.  On  the 
< Out-hnes,  a,  A lymphatic  veifel  belonging  to 
{ the  top  of  the  footi  b^  Its  firft  divifion  into 
( branches.*  c,-  c,  e,-  Other  divifions  of  the  fame 
‘ lymphatic  veffek  d,  A fmall  lymphatic  gland, 
e,  The  lymphatic  veffels  which  lie  between  the 
{kin  and  the  mufcles  of  the  thigh,  f f,  Two 
lymphatic  glands  at  the  upper  part  of  the  thigh 
below  the  groin,  g g,  Other  glands,  h,  A 
lymphatic  velTel  which  palfes  by  the  fide  of  thofe 
glands  without  communicating  with  them  ; and, 
bending  towards  the  infide  of  the  groin  at  (i), 
Opens  into  the  lymphatic  gland  (k).  1, 1,  Lyni*- 

phatie' glands  in  the  groin,  which  are  common 
to  the  lymphatic  veifels  of  the  genitals  and  thofe 
of  the  lower  extremity,  m,  n,  A ple!xus  of 
lymphatic  vellels  palling  on  the  infide  of  the  iliac 
artery. 


X 


Fig.  2. 


322 


OF  THE  ABDOMEN. 


Part  III. 


Fig.  2.  Exhibits  a Back  View  of  the  Lower  Ex- 
tremity, difledied  fo  as  to  fhow  the  deeper- 
feated  Lymphatic  Veflels  which  accompany 
the  arteries. 

A,  The  os  pubis.  B,  The  tuberofity  of  the  I 
ifchium.  C,  That  part  of  the  os  ilium  which 
was  articulated  with  the  os  facrum.  D,  The 
extremity  of  the  iliac  artery  appearing  above 
the  groin.  E,  The  knee.  F F,  The  two  cut 
furfaces  of  the  triceps  mufcle,  which  was  divid- 
ed to  fhow  the  lymphatic  veffels  that  pafs  through 
its  perforation  along  with  the  crural  artery.  G, 
The  edge  of  the  mufculus  gracilis.  H,  The  gaf- 
troncnemius  and  foleus,  much  fhrunk  by  being  | 
dried,  and  by  the  foleus  being  feparated  from 
the  tibia  to  expofe  the  veffels.  I,  The  heel. 
K,  The  foie  of  the  foot.  L,  The  fupefficial  j 
lymphatic  veffels  paffmg  over  the  knee,  to  get  | 
to  the  thigh.  On  the  out-lines  ; M,  The  pofte- 
rior  tibial  artery,  a,  A lymphatic  veffel  accom- 
panying the  poflerior  tibial  artery,  b.  The  fame 
veffel  croffmg  the  artery,  c,  A fmall  lymphatic 
gland,  through  which  this  deep-feated  lympha- 
fic  veffel  paffes.  d.  The  lymphatic  veffel  paf- 
fmg under  a fmall  part  of  the  foleus,  which 
is  left  attached  to  the  bone,  the  reft  being  re- 
moved. e.  The  lymphatic  veffel  crofting  the 
popliteal  artery,  f,  g,  h.  Lymphatic  glands  in 
the  ham,  through  which  the  lymphatic  veffel 
paffes.  i.  The  lymphatic  veffel  palfing  with 

the 


Part  III.  OF  THE  ABDOMEN.  323 

the  crural  artery,  through  the  perforation  of  the 
triceps  mufcle.  k,  The  lymphatic  veffel,  af- 
^ ter  it  had  palTed  the  perforation  of  the  triceps, 
dividing  into  branches  which  embrace  the  ar- 
< tery  (1).  m,  A lymphatic  gland  belonging  to 
I the  deep-feated  lymphatic  veffel.  At  this 
! place  thofe  veffels  pafs  to  the  fore-part  of-  the 
groin,  where  they  communicate  with  the  fuper- 
ficial  lymphatic  veffel  appearing  on  the  brim  of 
the  pelvis. 

Fig.  3.  Exhibits  the  Trunk  of  the  Human  Sub- 
ject prepared  to  fhow  the  Lymphatic  Veffels 
and  the  Du£tus  Thoracicus. 

^ A,  The  neck.  B B,  The  two  jugular  veins. 
I C,  The  vena  cava  luperior.  D D D D,  The 
I fubclavian  veins.  E,  The  beginning  of  the 
1 aorta,  pulled  to  the  left  fide  by  means  of  a liga- 
i ture,  in  order  to  fhow  the  thoracic  du6l  behind 
i it.  F,  The  branches  arifing  from  the  curvature 
I of  the  aorta.  G G,  The  two  carotid  arteries. 

[ H H,  The  firft  ribs,  1 1,  The  trachea.  K K, 
The  fpine.  L L,  The  vena  azygos.  M M, 
The  defcending  aorta.  N,  The  cceliac  artery, 
' dividing  into  three  branches.  O,  The  fuperior 
mefenteric  artery.  P,  The  right  crus  diaphrag- 
matis.  The  two  kidneys.  R,  The  right 

emulgent  artery.  S S,  The  external  iliac , arte- 
ries. g d.  The  mufculi  pfose.  T,  The  inter- 
nal iliac  artery.  U,  The  cavity  of  the  pelvis. 

X 2 XX,  The 


324  OF  THE  ABDOMEN.  Part  III, 

X X,  The  fpine  of  the  os  ilium.  Y Y,  The 
groins,  A lymphatic  gland  in  the  groin,  in- 
to which  lymphatic  veffels  from  the  lower  ex- 
tremity are  feen  to  enter,  bh^  The  lymphatic 
veffels  of  the  lower  extremities  paffing  under 
Poupart’s  ligament,  ec,  A plexus  of  the  lym- 
phatic veffels  lying  on  each  fide  of  the  pelvis, 
The  pfoas  mufcle  with  lymphatic  veffels  lying 
upon  its  infide.  A plexus  of  lymphatics, 
which  having  paffed  over  the  brim  of  the  pel- 
vis at  (e),  having  entered  the  cavity  of  the  pel- 
vis, and  received  the  lymphatic  veffels  belong- 
ing to  the  vifcera  contained  in  that  cavity,  next 
afcends,  and  paffes  behind  the  iliac  artery  to  (^). 

Some  lymphatic  veffels  of  the  left  fide  paf- 
fing over  the  upper  part  of  the  os  facrum,  to 
meet  thofe  of  the  right  fide,  The  right 
pfoas,  with  a large  plexus  of  lymphatics  lying  on 
its  infide.  h Z>,  The  plexus  lying  on  each  fide 
of  the  fpine.  i i /,  Spaces  occupied  by  the  lym- 
phatic glands,  The  trunk  of  the  lafteals, 
lying  on  the  under  fide  of  the  fuperior  mefente- 
ric  artery.  /,  The  fame  dividing  into  two 
branches,  one  of  which  paffes  on  each  fide  of 
the  aorta  ; that  of  the  right  fide  being  feen  to 
enter  the  thoracic  du£t  at  [ni).  The  thora- 
cic beginning  from  the  large  lymphatics, 

The  du6;  paffmg  under  the  lower  part  of  the  crus 
diaphragmatis,  and  under  the  right  emulgent  ar- 
tery. The  thoracic  dudl  penetrating  the 
'thorax,  Some  lymphatic  veffels  joining  that 

duff 


Part  III.  OF  THE  ABDOMEN.  325 

du£tin  the  thorax,  The  thoracic  duft  paF- 
fmg  under  the  curv^ature  of  the  aorta  to  get  to 
the  left  fubclavian  vein.  The  aorta  being  drawn 
afide  to  fhow  the  du£t.  r,  A plexus  of  lym- 
phatic veffels  pafling  upon  the  trachea  from  the 
thyroid  gland  to  the  thoracic  duft. 

Plate  XXVII. 

Fig.  I.  Reprefents  the  Under  and  Poilerior 
Side  of  the  Bladder  of  Urine,  &c. 

a,  The  bladder,  bb.  The  infertion  of  the 
iiterers,  c c.  The  vafa  deferentia,  which  con- 
vey the  femen  from  the  tefticles  to  d d,  The  ve- 
ficulT  feminales,-^ — >and  pais  through  e,  The  pro- 
ftate  gland,  to  difcharge  themfelves  into  f,  The 
beginning  of  the  urethra. 

Fig.  2.  A tranfverfe  Sedion  of  the  Penis. 

g g.  Corpora  carvernofa  penis,  h.  Corpus 
cavernofum  urethrse.  i.  Urethra,  k,  Septum 
penis.  1 1,  The  feptum  between  the  corpus  ca- 
vernofurn  urethrte  and  that  of  the  penis. 

Fig.  3,  A longitudinal  Sedtion  of  the  Penis 

m m.  The  corpora  carvernofa  penis,  divided 
by  o.  The  feptum  penis,  n.  The  corpus  ca- 
vernofum  glandis,  which  is  the  continuation  of 
that  of  the  urethra. 


Fig.  a. 


Part  III. 


326  OF  THE  ABDOMEN. 

Fig.  4.  Reprefents  the  Female  Organs  of  Ge- 
neration. 

a,  That  fide  of  the  uterus  which  is  next  the 
os  facrum.  i , Its  fundus.  2,  Its  cervix,  b b, 
The  Fallopian  or  uterine  tubes,  which  open  in- 
to the  cavity  of  the  uterus  ; — but  the  other  end 
is  open  within  the  pelvis,  and  fu  ' ounded  by 
c c,  The  fimbrise.  d d.  The  ovaria.  e.  The 
os  internum  uteri,  or  mouth  of  the  womb,  f f. 
The  ligamenta  rotunda,  which  paffes  without  the 
belly,  and  is  fixed  to  the  labia  pudendi.  g g.  The 
cut  edges  of  the  ligamenta  lata  which  connects 
the  uterus  to  the  pelvis,  h,  The  infide  of  the 
vagina,  i.  The  orifice  of  the  urethra,  k.  The 
clitoris  furrounded  by  (1,)  The  prseputium. 
m m.  The  labia  pudendi.  n n.  The  nympho. 

Fig.  5,  Shows  the  Spermatic  Dudls  of  theTef- 
ticle  filled  with  Mercury. 

A,  The  vas  deferens.  B,  Its  beginning, 
which  forms  the  pofterior  part  of  the  epididy- 
misi  C,  The  middle  of  the  epididymis,  com- 
pofed  of  ferpentine  du£ts.  D,  The  head  or  an- 
terior part  of  the  epididymis  unravelled,  e e e e, 
T he  whole  dudls  which  compofe  the  head  of 
the  epiddiymis  unravelled,  f f.  The  vafa  defe- 
rentia.  g g,  Rete  tefiis.  h h,  Some  redilineal 

duds 


Plate  MVI 


€ 


Plate  ZZV 11 


Part  III. 


OF  THE  ABDOMEN. 


327 


duds  which  fend  off  the  vafa  deferentia.  i i. 
The  fubftance  of  the  tefticle. 

Fig.  6.  The  right  Tefticle  entire,  and  the  Epi- 
didymis filled  with  Mercury. 

A,  The  beginning  of  the  vas  deferens.  B, 
The  vas  deferens  afcending  towards  the  abdomen. 
C,  The  pofterior  part  of  the  epididymis,  named 
globus  minor.  D,  The  fpermatic  veflels  inclofed  in 
cellular  fubftance.  E,  The  body  of  the  epidy- 
dimis.  F,  Its  head,  named^/o^z/j-  major.  G,  Its 
beginnning  from  the  tefticle.  H,  The  body  of 
the  tefticle,  inclofed  in  the  tunica  albuginea 


PART  IV, 


, Of:  TTORiiS. 


52  a 

P A R T IV. 

OF  THE  THORAX, 

^ I "^HE  THORAX,  or  CHEST,  is  that  cavity 
j§_  of  the  tr,un|c  whicji  e^jids  from  the  cla- 
vicles, or  the  lower  paj:t  of  tjji.e  ppcjk,  tp  dia- 
phrag^H,  .and  tAclwdes  the  vha|  prgaas,  .'F'diich 
are  the  heart  and  lui>ga  ; atiddikewife  t^e  tE4“ 
chea  and  aTophagus.— This  cavity  h formed  j>y 
the  ribs  and  vertebras  of  the  bac^,  covered  by  a 
great  number  of  mulcles^  adfJ  eoptlPPii 

integumejrt!?|>  ai^td  anteriorly  by  two  glapdolar 
bodies  called  the  hreajls.  The  fpaces  between 
the  ribs  are  filled  by  the  mufcular  fibres,  which  1 
from  their  fituation  are  called  mtercojlal  mufcles. 

Sect.  I.  Of  the  Breajls. 

'Fhe  h‘eafs  may  be  defined  to  be  two  large 
conglomerate  glands,  mixed  with  a good  deal  of  ^ 
adipofe  membrane.  The  glandular  part  is  com- 
pofed  of  an  infinite  number  of  minute  arteries,  [ 
veins,  and  nerves. 

The  arteries  are  derived  from  two  different 
trunks  ; one  of  which  is  called  the  internal^  and 
the  other  the  external^  mawmary  artery.  The 
firft  of  thefe  arifes  from  the  fubclavian,  and  the 
latter  from  the  axillary, 


The 


Pai^tIV.  of  the  thorax.  329 

The  ¥eins  every  where  accompany  the  arte- 
ries, and  are  diftinguiflred  by  the  lame  name. 
Tlie  iiervesi  are  chiefly  from  the  vertebral  pairs. 
Like  all  other  conglomerate  glands,  the  breafts 
are  made  up  of  a great  many  fmall  diftinci  glands, 
m which  tire  milk  is  fecreted  from  the  ultimate 
branches  of  arteries.  The  excretory  duds  of 
thefe  feveral  glands  gradually  uniting  as  they  ap^t 
proach  the  nipple,  form  the  tubuii  ladiferi, 
which  are  ufually  more  than  a dozen  in  number, 
and  open  at  its  apex,  but  have  little  or  no  com- 
munication, as  has  been  fuppoled,  at  the  root  of 
the  nipple.  Thefe  duds:,  in  liieir  courte  from  the 
glands,  are  furrounded  by  a ligamentaiy  elaftic 
fubftance,  which  terminates  with  them  in  the 
nipple.  Both  this  fubPrance,  and  the  duds 
which  it  contains,  are  capable  of  conliderable 
extenfion  and  contradion  5 but  in  their  natural 
ftate  are  moderately  corrugated,  fo  as  to  prevent 
an  involuntary  flow  of  milk,  uniefs  the  diftendr- 
ing  force  be  very  great  from  the  accumulation  of 
too  great  a quantity. 

The  whole  fubftance  of  the  nipple  is  very 
fpongy  and  elalfic  : its  external  furfaee  is  une- 
ven, and  full  of  fmall  tubercles.  I'he  nipple  is 
ftirrounded  with  a difk  or  circle  of  a diiferent 
colour,  called  tfte  ai'eola ; and  on  the  inftde  of 
the  fkin,  under  the  areola,  are  many  febaceous 
glands,  which  pour  out  a mucus  to  defend  the 
areola  and  nipple  ; for  the  fl^in  upon  thefe  parts 

is 


330  OF  THE  THORAX.  Part  IV. 

is  very  thin ; and  the  nervous  papillae  lying  very 
bare,  are  much  expofed  to  irritation. 

The  breafts  are  formed  for  the  fecretion  of 
milk,  which  is  deftined  for  the  nourifhment  of 
the  child  for  fome  time  after  its  birth.  This  fe- 
cretion begins  to  take  place  foon  after  delivery, 
and  continues  to  flow  for  many  months  in  very 
large  quantities,  if  the  woman  fuckles  her  child. 

The  operation  of  fudion  depends  on  the  prin- 
ciples of  the  air-pump,  and  the  flow  of  milk 
through  the  ladiferous  tubes  is  facilitated  by  their 
being  ftretched  out. 

The  milk,  examined  chemically,  appears  to 
be  compofed  of  oil,  mucilage,  and  water,  and 
of  a confiderable  quantity  of  fugar.  The  ge- 
nerality of  phyfiologifts  have  fuppofed  that,  like 
the  chyle,  it  frequently  retains  the  properties  of 
the  aliment  and  medicines  taken  into  the  flo- 
mach ; but  from  fome  late  experiments  this 
luppofition  appears  to  be  ill-founded. 

Sfct.  II.  Of  the  Pleura. 

The  cavity  of  the  thorax  is  every  where  lin- 
ed by  a great  membrane  of  a firm  texture  call- 
ed pleura.  It  is  compofed  of  two  diftind  porti- 
ons or  bags,  which,  by  being  applied  to  each 
other  laterally,  form  a feptum  called  mediafinum; 

which 


* Journ.  de Med.  1781. 


Part  IV.  OF  THE  THORAX.  331 

which  divides  the  cavity  into  two  parts,  and  is 
attached  pofterioriy  to  the  vertebrse  of  the  back, 
and  anteriorly  to  the  fternum.  But  the  two  la- 
minae of  which  this  feptum  is  formed,  do  not 
every  where  adhere  to  each  other  ; for  at  the 
lower  part  of  the  thorax  they  are  feparated,  to 
afford  a lodgement  to  the  heart ; and  at  the  upper 
part  of  the  cavity,  they  receive  between  them 
the  thymus. 

The  pleura  is  plentifully  fupplied  with  arte- 
ries and  veins  from  the  internal  mammary  and 
the  intercoftals.  Its  nerves,  which  are  very  in- 
confiderable,  are  derived  chiefly  from  the  dorfal 
and  intercoftal  nerves. 

The  furface  of  the  pleura,  like  that  of  the  pe- 
ritonaeum and  other  membranes  lining  cavities, 
is  conftantly  bedewed  with  a ferous  moifture  (w) 
which  prevents  adhefion  of  the  vifcera. 

The  mediaflinum,  by  dividing  the  breaft  into 
two  cavities,  obviates  many  inconveniences,  to 
which  we  fhould  otherwile  be  liable.  It  pre- 
vents the  two  lobes  of  the  lungs  from  compref- 
fmg  each  other  when  we  lie  on  one  fide ; and 
confequently  contributes  to  the  freedom  of  ref- 
piration,  which  is  difturbed  by  the  leafl:  preffure 
on  the  lungs.  If  the  point  of  a fword  pene- 
trates between  the  ribs  into  the  cavity  of  the  tho- 
rax, the  lungs  on  that  fide  ceafe  to  perform  their 

office ; 

(w)  When  this  fluid  is  exhaled  in  too  great  a quantity,  or 
is  not  properly  carried  off,  it  accumulates  and  conftltutes 
the  hydrops  peftoris. 


332  OF  THE  THORAX.  Part  IV. 

oflice ; becaufe  the  air  being  admitted  through 
the  wound,  prevente  the  dil^ation  of  that  lobe ; 
while  the  other  lobe,  which  is  feparated  from  it 
by  the  rnediaftinum,  remains  unhurt,  and  con^ 
tinues  to  perform  its  funSion  as  ufual. 

Sect.  II.  Of  the  Thymus. 

The  thymus  is  a glandular  fubftance,  the  ufe 
of  which  is  not  perfectly  afcertained,  its  excre- 
tory du^  not  having  yet  been  difcovered.  It  is 
of  an  objong  figure,  and  is  larger  in  the  foetus 
and  in  yofing  children  than  in  adults,  being  fome- 
times  nearly  effaced  in  very  old  fubje£ts.  It  is 
placed  in  the  upper  part  of  the  thorax,  between 
the  two  laminse  of  the  rnediaftinum  ; but  at  firft 
is  not  altogether  contained  within  the  cavity  of 
the  cheft,  being  found  to  border  upon  the  upper 
e?ftremity  of  the  fternum. 

Sect.  IV.  Of  the  Diaphragm. 

The  cavity  of  the  thorax  is  feparated  from  that 
of  the  addomen,  by  a flefhy  and  membranous 
fubftance  called  the  diaphragm  or  midriff.  The 
greateft  part  of  it  is  compofed  of  mufcular  fibres ; 
and  on  this  account  fyftematic  writers  ufually 
place  very  properly  among  the  mufcles.  Its  mid*- 
die  part  is  tendinous,  and  it  is  covered  by  the 
pleura  above,  and  by  the  peritonseum  below. 
It  feems  to  have  been  improperly  named  feptum 


Part  IT.  Of  THE  THORAX.  333 

tranfuerfum^  as  it  does  not  make  a plane  tranf- 
verie  divifion  of  the  two  cavities,  but  forms  a 
kind  of  vault,  the  fore-part  of  which  is  attach- 
ed to  the  fternum.  Laterally  it  is  fixed  to  the 
laft  of  the  true  ribs,  and  to  all  the  falfe  ribs ; and 
its  lower  and  pofterior  part  is  attached  to  the 
vertebrae  lumborum,  where  it  may  be  faid  to  be 
divided  in  two  portions  or  crura  (x). 

The  principal  arteries  of  the  diaphragm  are 
derived  from  the  aorta,  and  its  veins  pafs  into 
the  vena  cava.  It  nerves  are  chiefly  derived 
from  the  cervical  pairs.  It  affords  a paffage  to 
the  vena  cava  through  its  tendinous  part,  and  to 
the  oefophagus  through  its  flefhy  portion.  TI  e 
aorta  paffes  down  behind  it  between  its  cura. 

The  diaphragm  not  only  ferves  to  divide  the 
thorax  from  the  abdomen,  but  by  its  mufcular 
ftrudlure  is  is  rendered  one  of  the  chief  agents 
in  refpirationi.  When  its  fibres  contract,  its 
convex  fide,  which  is  turned  towards  the  tho- 
rax, becomes  gradually  flat,  and  by  increafing 
the  cavity  of  the  breaft,  affords  room  for  a com- 
plete dilatation  of  the  lungs,  by  means  of  thn 
air  which  is  then  drawn  into  them  by  the  a<T  of 
infpiration.  The  fibres  of  the  diaphragm  thefl 
relax  5 and  as  it  refumes  its  former  Rate,  the  ca- 
vity 

(x)  Anatomical  "writers  have  ufnally  defcrlbed  the  dia- 
phragm as  being  made  up  of  two  mufcles  united  by  a middle 
tendon  ; and  thefe  two  portions  or  crura  form  what  they 
•fpeak  of  as  the  inferior  mufcles  arifmg  from  the  fidcs  and 
fore  part  of  the  vertebrse. 


334  OF  THE  THORAX.  Part  IV. 

vity  of  thorax  becomes  gradually  diminifhed, 
and  the  air  is  driven  out  again  from  the  lungs  by 
a motion  contrary  to  the  former  one,  called  ex- 
fplration. 

It  is  in  fome  meafure,  by  means  of  the  dia- 
phragm, that  we  void  the  fseces  at  the  anus,  and 
empty  the  urinary  bladder.  Befides  thefe  offices, 
the  ad:s  of  coughing,  fneezing,  fpeaking,  laugh- 
ing, gaping,  and  fighing,  could  not  take  place 
without  its  affiftance  ; and  the  gentle  preffure 
which  all  the  abdominal  vifcera  receive  from  its 
conftant  and  regular  motion,  cannot  fail  to  affift 
in  the  performance  of  the  feveral  fundions  which  I 
were  afcribed  to  thofe  vifcera. 

Slot.  V.  Of  the  Trachea.  :i 

The  trachea  or  windpipe,  is  a cartilaginous  i 
and  membranous  canal,  through  which  the  air  i 
paffes  into  the  lungs.  Its  upper  part,  which  is 
called  the  larynx.,  is  compofed  of  five  cartilages. 
The  uppermoft  of  thefe  cartilages  is  placed  over 
the  glottis  or  mouth  of  the  larynx,  and  is  called 
epiglottis.,  which  has  been  before  fpoken  of,  as 
clofing  the  paffage  to  the  lungs  in  the  a6t  of  ^ 
fwallowing.  At  the  fides  of  the  glottis  are 
placed  the  two  arytenoide  cartilages,  which  are 
of  a very  complex  figure,  not  eafy  to  be  de- 
fcrihed.  The  anterior  and'  larger  part  of  the 
larynx  is  made  up  of  two  cartilages ; one  of 
v’^hich  is  called,  thyroides  or  fcutiformis.,  from  its 

being 


Part  IV.  OF  THE  THORAX.  335 

being  ftiaped  like  a buckler ; and  the  other  C7'U 
coides  or  annularis^  from,  its  refembling  a ring. 
Both  thefe  cartilages  may  be  felt  immediately 
under  the  fkin,  at  the  fore-part  of  the  throat, 
and  the  thyroides,  by  its  convexity,  forms  an 
eminence  called  pomum  adami^  which  is  ufually 
more  confiderable  in  the  male  than  in  the  female 
fubjed. 

All  thefe  cartilages  are  united  to  each  other  by 
means  of  very  elaftic,  ligamentous  fibres ; and 
are  enabled,  by  the  affiftance  of  their  feveral 
I mufcles,  to  dilate  or  contrad  the  paflage  of 
f the  larynx,  and  to  perform  that  variety  of  mo- 
1 tion  which  feems  to  point  out  the  larynx  as  the 
1 principal  organ  of  the  voice  ; for  when  the  air 
pafTes  out  through  a wound  in  the  trachea,  it  pro- 
duces no  found. 

Thefe  cartilages  are  moiftened  by  a mucus, 
which  feems  to  be  fecreted  by  minute  glands  fi- 
tuated  near  them.  The  upper  part  of  the  trachea 
is  covered  anteriorly  and  laterally  by  a confider- 
able  body,  which  is  fuppofed  to  be  of  a glandu- 
lar ftrudure,  and  from  its  fituation  near  the  thy- 
roid cartilage  is  called  the  thyroid  gland;  though 
its  excretory  dud  has  not  yet  been  difcovered, 
or  its  ufe  afcertained. 

The  glottis  is  interiorly  covered  by  a very  fine 
membrane,  which  is  moiftened  by  a conftant 
fupply  of  a watery  fluid.  From  the  larynx  the 
canal  begins  to  take  the  name  of  trachea  or  af- 
pera  arteria^  and  extends  from  thence  as  far  down 


1 


■;o  OF  THE  THORAX.  Part  IV. 

RS  tlie  third  or  fourth  veftebra  of  {he  baek^  where 
it  divides  into  two  branches^  which  at'e  the  right 
and  left  bronchial  tube.  Each  of  thefe  brcmehi 
(y)  ramifies' through  the  fubfisanc€  of  that  lobe 
of  the  lungs  to  which  it  is  diftributed,.by  in  in- 
finite rm-mber  of  branches,,  which  are  formed  of 
cartilages  feparated  from-  each  other  like  thofe  of 
the  trachea,  by  an  intervening  membranous:  afid 
ligamentary  fubftanee.  Each  of  thefe  cartilages 
is  of  an  angular  figure  ^ and  as  t-hey  become  gra- 
dually lefs  and  Ids  in-  their  diameter,-  the  lower 
ones  are  in  fome  meafure  received  into  th-ofe 
above  tliem,-  when  the  lungs^  after  being  infiaf-* 
ed,  gradually  coilapfe  by  the-  air  being  pufbed 
out  from  them  in  exfpiration.  As  the  bra-nel^s  j 
of  tire  bronchi  becotn'e  more  minut-e.  their  i&r-  I 
tilages  become  more  and  more  angu-lan  and  memu 
branous,  till  at  length  they  are  found  to  be  per- 
fectly membranous,  and- at  laft  become  invifible-f 
The  trachea  is  furn-ifhed  with  fldhy  or  muf* 
cular  fibres ; fome  of  which  p'afs  through  iw  j 
whole  extent  longit-ud-maHy^  while  the  othefs 
are  carried  round  it  in  a circmlar  direction  5 fo 
that  by  the  contraction  or  relaxation  of  thefe  fi- 
bres, 

2 

(y)  The  right  bronchial  tube  is  ufually  found  to  be  fome- 
■\r hat  Oiorter  and  thicker  fh'ail  the  left  j and  M.  Portal,  who  ^ 
has  pubiifhed  a'  memoir  on'  the  aCfioil  of  t'he  lungs  on  thli^. 
aorta  in  refpiration,-  obferves,  that  the  left  bronchial  tube  is 
dofely  connected  by'  the  aorta ; and  from  fome  experiments 
he  is  iriduced  to  conclude,  that  in  the  firfl  refpirations,  the 
air  only  enters  irit-o  the  right  lobe  of  the  lungs.  M^fTtbirc.^ 

Je  /’  Acadc.niie  Royale  des  Sciences,  1 769. 


Part  IV.  OF  THE  THORAX.  337 

bres,  it  is  enabled  to  fliorten  or  lengthen  itfelf, 
and  likewife  to  dilate  or  contrad;  the  diameter  of 
its  paffage. 

The  trachea  and  its  branches,  in  all  their  ra- 
mifications, are  furnifhed  with  a great  number  of 
fmall  glands  which  are  lodged  in  their  cellular 
fubftance,  and  difcharge  a mucous  fluid  on  the 
inner  furface  of  thefe  tubes. 

The  cartilages  of  the  trachea,  by  keeping  it 
conftantly  open,  afford  a free  palfage  to  the  air, 
which  we  are  obliged  to  be  incelfantly  refpiring ; 
and  its  membranous  part,  by  being  capable  of 
contraction  and  dilatation,  enables  us  to  receive 
and  expel  the  air  in  a greater  or  lefs  quantity, 
and  with  more  or  lefs  velocity,  as  may  be  requir- 
ed in  flinging  or  in  declamation.  This  membran- 
ous ftrudure  of  the  trachea  pofteriorly,  fleems 
likewife  to  affift  in  the  defeent  of  the  food,  by 
preventing  that  impediment  to  its  paffage  down 
the  oefophagus,  which  might  be  expeCted  if  the 
cartilages  were  complete  rings. 

The  trachea  receives  its  arteries  from  the  ca- 
rotid and  fubclavian  arteries,  and  its  veins  pafls 
into  the  jugulars.  Its  nerves  arifle  from  the  re- 
current branch  of  the  eighth  pair,  and  from  the 
Cervical  plexus. 

Sect.  VI.  0/'  the  Lungs. 

The  lungs  fill  the  greater  part  of  the  cavity  of 
the  breaft.  They  are  of  a foft  and  flpongy  tex- 

Y ture. 


33^  Ol^  THE  TH0R4X.  Part  IV. 

ture,  and  are  divided  into  two  lobes^  which  are 
feparated  from  each  other  by  the  mediaftinum, 
and  are  externally  covered  by  a pfodudion  of 
the  pleura.  Each  of  thefe  is  divided  into  two 
or  three  feffer  lobes  ; and  we  commonly  find 
three  in  the  right  fide  of  the  cavity,  and  two  in 
the  left. 

To  difeover  the  ftmdure  of  the  lungs,  it  is 
required  to  follow  the  ramifications  of  the  bron- 
chi, which  were  deferibed  in  the  laft  fedtion. 
Thefe  becoming  gradually  more  and  more  mi- 
nute, at  length  terminate  in  the  cellular  fpaces  or 
veficles,  which  make  up  the  greateft  part  of  the 
fubftance  of  the  lungs,  and  readily  communicate 
with  each  other. 

The  lungs  feem  to  poflefs  but  little  fenfibility. 
Their  nerves,  which  are  fmall,  and  few  in  num- 
ber, are  derived  from  the  intercoftal  and  eighth 
pair.  This  laft  pair  having  reached  the  thorax, 
fends  off  a branch  on  each  fide  of  the  trachea, 
called  the  reeurrent^  which  reafeends  at  the  back 
of  the  trachea,  to  which  it  furnifhes  branches  in 
its  afeent,  as  w^ell  as  to  the  oefophagus,  but  it  is 
chiefly  diftributed  to  the  larynx  and  its  muffles. 
By  dividing  the  recurrent  and  fuperior  laryngeal 
nerves  at  their  origin,  an  animal  is  deprived  of 
its  voice. 

There  are  two  feries  of  arteries  which  carry 
blood  to  the  lungs  : thefe  are  the  arterise  bron- 
chiales,  and  the  pulmonary  arteiy. 

The 


Part  IV.  OF  THE  THORAX.  339 

The  arteriae  bronchiales  begin  ufually  by  two 
branches ; one  of  which  commonly  arifes  from 
the  right  intercoftal,  and  the  other  from  the  trunk 
of  the  aorta : but  fometimes  there  are  three  of 
thefe  arteries,  and  in  fome  fubjeds  only  one. 
The  ufe  of  thefe  arteries  is  to  ferve  for  the  riou- 
rifhment  of  the  lungs,  and  their  ramifications  are 
feen  creeping  every  where  on  the  branches  of  the 
bronchi.  The  blood  is  brought  back  from  them 
by  the  bronchial  vein  into  the  vena  azygos. 

The  pulmonary  artery  and  vein  are  not  in- 
tended for  the  nourifhment  of  the  lungs  ; but 
the  blood  in  its  paflage  through  them  is  deftined 
to  undergo  fome  changes,  or  to  acquire  certain 
eflential  properties  (from  the  action  of  the  air), 
which  it  has  loft  in  its  circulation  through 
the  other  parts  of.  the  body.  The  pulmo- 
nary artery  receives  the  blood  from  the  right 
ventricle  of  the  heart,  and  dividing  into  two 
branches,  accompanies  the  bronchi  every  where, 
by  its  ramifications  through  the  lungs  ; and  the 
blood  is  afterwards  conveyed  back  by  the  pulmo- 
nary vein,  which  gradually  forming  a confider- 
able  trunk,  goes  to  empty  itfelf  intb  the  left 
ventricle  of  the  heart ; fo  that  the  quantity  of 
blood  which  enters  into  the  lungs,  is  perhaps 
greater  than  that  which  is  fent  in  the  fame  pro- 
portion of  time  through  all  the  other  parts  of 
the  body. 


'340 


OF  THE  THORAX. 


Part  IV. 


Sect.  VII.  Of  Refpiralion. 

Respiration  conftitutes  one  of  thofe  func- 
tions which  are  properly  termed  vital,  as  being 
elfential  to  life  j for  to  live  and  to  breathe  are  in 
fa(T  fynonyraous  terms.  It  confifts  in  an  alter- 
nate contraftion  and  dilatation  of  the  thorax,  by 
firft  infpiring  air  into  the  lungs,  and  then  expell- 
ing it  from  them  in  exfpiration. 

It  will  perhaps  be  eafy  to  diftinguifh  and  point 
out  the  feveral  phenomena  of  refpiration ; but 
to  explain  their  phyfical  caufe  will  be  attended 
with  difficulty  : for  it  will  naturally  be  enquir- 
ed, how  the  lungs,  when  emptied  of  the  air, 
and  contracted  by  exfpiration,  become  again  in- 
flated, they  themfelves  being  perfectly  paffive  ? 
How  the  ribs  are  elevated  in  oppofition  to  their 
own  natural  fituation  ? and  why  the  diaphragm 
is  contracted  downwards  towards  the  abdomen  ? 
Were  we  to  alfert  that  the  air,  by  forcing  its  way 
into  the  cavity  of  the  lungs,  dilated  them,  and 
confequently  elevated  the  ribs,  and  prelfed  down 
the  diaphragm,  we  fhould  fpeak  erroneoufly. 
What  induces  the  firft  infpiration,  it  is  not  eafy 
to  afcertain  ; but  after  an  animal  has  once  refpir- 
ed,  it  would  feem  likely  that  the  blood,  after  ex* 
Ipiration,  finding  its  paflage  through  the  lungs 
obftruCled,  becomes  a llimulus,  which  induces 
the  intercoftal  mufcles  and  the  diaphragm  to  con- 
iraCl',  and  enlarge  the  cavity  of  the  thorax,  in 

Gonfequence 


Part  IV.  OF  THE  THORAX.  341 

confequence  perhaps  of  a certain  nervous  influ- 
ence, which  we  will  not  here  attempt  to  explain. 
The  air  then  rufhes  into  the  lungs  ; every  branch 
of  the  bronchial  tubes,  and  all  the  cellular  fpaces 
into  which  they  open,  become  fully  dilated ; 
and  the  pulmonary  veifels  being  equally  diftend- 
ed,  the  blood  flows  through  them  with  eafe.  But 
as  the  ftimulus  which  firfl;  occafioned  this  dila- 
tation ceafes  to  operate,  the  mufcles  gradually 
contraft,  the  diaphragm  rifes  upwards  again,  and 
diminifhes  the  cavity  of  the  cheft ; the  ribs  re- 
turn to  their  former  Rate  ; and  as  the  air  palfes 
out  in  exfpiration,  the  lungs  gradually  collapfe, 
and  a refiftance  to  the  palTage  ot  the  blood  again 
takes  place.  But  the  heart  continuing  to  receive 
and  expel  the  blood,  the  pulmonary  artery  be- 
gins again  to  be  diftended,  the  ftimulus  is  re- 
newed, and  the  fame  procefs  is  repeated,  and 
continues  to  be  repeated,  in  a regular  fucceffion, 
during  life  : for  though  the  mufcles  of  relpiration, 
having  a mixed  motion,  are  (unlike  the  heart) 
in  fome  meafure  dependent  on  the  will,  yet  no 
human  being,  after  having  once  refpired,  can 
live  many  moments  without  it.  In  an  attempt 
to  hold  one’s  breath,  the  blood  foon  begins  to 
diftend  the  veins,  which  are  unable  to  empty 
their  contents  into  the  heart ; and  we  are  able 
only,  during  a very  little  time,  to  refift  the  fti- 
mulus to  infpiration.  In  drowning,  the  circu- 
lation feems  to  be  ftopped  upon  this  principle  ; 
and  in  hanging,  the  preflTure  made  on  the  jugu- 
lar 


342  OF  THE  THORAX.  Part  IV. 

lar  veins,  may  co-operate  with  the  ftoppage  of 
refpiration  in  bringing  on  death. 

Till  within  thefe  few  years  phyfiologifts  were 
entirely  ignorant  of  the  ufe  of  refpiration.  It 
was  at  length  difcovered  in  part  by  the  illuftrious 
Dr.  Prieftley.  He  found  that  the  air  exfpired 
by  animals  was  phlogifticated  ; and  that  the  air 
was  fitter  for  refpiration,  or  for  fupporting  ani- 
mal life,  in  proportion  as  it  was  freer  from  the 
phlogiftic  principle.  It  had  long  been  obferv- 
ed,  that  the  blood  in  paffing  through  the  lungs 
acquired  a more  florid  colour.  He  therefore 
fufpefted,  that  it  was  owing  to  its  having  im- 
parted phlogifton  to  the  air  : and  he  fatisfied 
himfelf  of  the  truth  of  this  idea,  by  experi- 
ments, which  fhowed,  that  the  craflamentum  of 
extravafated  blood,  phlogifticated  air  in  propor- 
tion as  it  loft  its  dark  colour.  He  farther  found, 
that  blood  thus  reddened  had  a ftrong  attra(ftion 
for  phlogifton  ; infomuch  that  it  was  capable  of 
taking  it  from  phlogifticated  air,  thereby  becom- 
ing of  a darker  colour.  From  hence  it  appeared 
that  the  blood,  in  its  circulation  through  the  ar- 
terial fyftem,  imbibes  a confiderable  quantity  of 
phlogifton,  which  is  difcharged  from  it  to  the 
air  in  the  lungs. 

This  difcovery  has  fince  been  profecuted  by 
two  very  ingenious  phyfiologifts.  Dr.  Crawford 
and  Mr.  Elliot.  It  had  been  fhown  by  profef- 
fors  Black  and  Irvine,  that  different  bodies  have 
differertt  capacities  for  containing  fire.  For  ex- 
ample, 


Part  IV.  OF  THE  THORAX.  343 

ample,  that  oil  and  water,  when  equally  hot  to 
the  fenfe  and  the  thermometer,  contain  different 
proportions  of  that  principle  ; and  that  unequal 
quantities  of  it  are  required,  in  order  to  raife 
thofe  fubftances  to  like  temperatures.  The  en- 
quiries of  Dr.  Crawford  and  JVi  r.  Elliot  tend  to 
prove,  that  the  capacities  of  bodies  for  contain- 
ing fire  are  diminifhed  by  the  addition  of  phlo- 
gifton,  and  increafed  by  its  feparation  ; the  ca- 
pacity of  calx  of  antimony,  for  example,  being 
greater  than  that  of  the  antimony  idelf.  Com- 
mon air  contains  a great  quantity  of  fire  ; com- 
buftible  bodies  very  little.  In  combuftion,  a 
double  elective  attraction  takes  place  ; the  phlo- 
gifton  of  the  body  being  transferred  to  the  air, 
the  fire  contained  in  the  air  to  the  combuftible 
body.  But  as  the  capacity  of  the  latter  is  not 
increafed  fo  much  as  that  of  the  former  is  dimi- 
niflied,  only  part  of  the  extricated  fire  will  be 
abforbed  by  the  body.  The  remainder  therefore 
will  raife  the  temperature  of  the  compound  ; and 
hence  we  may  account  for  the  heat  attending^ 
combuftion.  As  the  ufe  of  refpiration  is  to 
dephlogifticate  the  blood,  it  feems  probable,  that 
a like  double  eleClive  attraction  takes  place  in 
this  procefs  ; the  phlogifton  of  the  blood  being 
transferred  to  the  air,  and  the  fire  contained  in 
the  air  to  the  blood ; but  with  this  difference, 
that  the  capacities  being  equal,  the  whole  of  the 
extricated  fire  is  abforbed  by  the  latter.  The 
blood  in  this  ftate  circulating  through  the  body, 

imbibes 


344  OF  THE  THORAX.  Part  IV. 

imbibes  phlogifton,  and  of  coiirfe  gives  out  its 
fire  ; part  only  of  which  is  abforbed  by  the  parts 
furnifhing  the  phlogifton  ; the  remainder,  as  in 
combuftion,  becoming  fenfible  ; and  is  therefore 
the  caufe  of  the  heat  of  the  body,  or  what  is 
called  animal  heat. 

In  confirmation  of  this  doctrine  it  may  be 
obferved,  that  the  venous  blood  contains  lefs 
fire  than  the  arterial ; combuftible  bodies  lefs 
than  incombuftible  ones  ; and  that  air  contains 
lefs  of  this  principle,  according  as  it  is  rendered, 
by  combination  with  phlogifton,  lefs  fit  for  ref- 
piration  (z). 

In  afcending  very  high  mountains,  refpiration 
is  found  to  become  fhort  and  frequent,  and  fome- 
times  to  be  attended  with  a fpitting  of  blood. 
Thefe  fymptoms  feem  to  be  occafioned  by  the 
air  being  too  rare  and  thin  to  dilate  the  lungs 
fufficiently  ; and  the  blood  gradually  accumulat- 
ing in  the  pulmonary  veflels,  fometimes  burfts 
through  their  coats,  and  is  brought  up  by  cough- 
ing. This  has  likewife  been  accounted  for  in  a 
different  way,  by  fuppofmg  that  the  air  contain- 
ed in  the  blood,  not  receiving  an  equal  preffure 
from  that  of  the  atmofphere,  expands,  and  at 
length  ruptures  the  very  minute  branches  of  the 
pulmonary  veffels  ; upon  the  fame  principle  that 
fruits  and  animals  put  under  the  receiver  of  an 

airr 

(z)  See  Crawford’s  Experiments  and  Obfervations  on 
Animal  Heat,  and  Elliot’s  Philolophical  Obfervations- 


Part  IV.  OF  THE  THORAX.  345 

air-pump,  are  feen  to  fwell  as  the  outer  air  be- 
comes exhaufted.  But  Dr.  Darwin  of  Litchfield 
has  lately  publifhed  fome  experiments,  which 
feem  to  prove,  that  no  air  or  elaftic  vapour  does 
exift  in  the  blood-veflels,  as  has  been  generally 
fiippofed  : and  he  is  induced  to  impute  the  fpit- 
ting  of  blood,  which  has  fometimes  taken  place 
in. afcending  high  mountains,  to  accident,  or  to 
violent  exertions  ; as  it  never  happens  to  animals 
that  are  put  into  the  exhaufted  receiver  of  an  air- 
pump,  where  the  diminution  of  preflure  is  ma- 
ny times  greater  than  on  the  fummit  of  the  high- 
eft  mountains. 

Sect.  VIII.  Of  the  Voice. 

Respiration  has  already  been  defcribed  as 
affording  us  many  advantages  ; and  next  to  that 
of  life,  its  moft  important  ufe  feems  to  be  that 
of  forming  the  voice  and  fpeech.  The  ancients, 
and  almoft  all  the  moderns,  have  confidered  the 
organ  of  fpeech  as  a kind  of  mufical  inftrument, 
which  may  be  compared  to  a flute,  to  an  hautr- 
boy,  to  an  organ,  &c.  and  they  argue  after  the 
following  manner. 

The  trachea,  which  begins  at  the  root  of  the 
tongue,  and  goes  to  terminate  in  the  lungs,  may 
be  compared  to  the  pipe  of  an  organ  the  lungs  di- 
lating like  bellows  during  the  time  of  infpiration  ; 
and  as  the  air  is  driven  out  from  them  in  exfpi- 
rafion,  it  finds  its  paffage  ftraitened  by  the  carti- 
lages 


34(5  OF  THE  THORAX.  Part  IV. 

lages  of  the  larynx,  againft  which  it  ftrikes.  As 
thefe  cartilages  are  more  or  lefs  elaftic,  they  occa- 
fion  in  their  turn  more  or  lefs  vibration  in  the 
air,  and  thus  produce  the  found  of  the  voice ; 
the  variation  in  the  found  and  tone  of  which  de- 
pends on  the  hate  of  the  glottis,  which,  when 
ftraitened,  produces  an  acute  tone,  and  a grave 
one  when  dilated. 

The  late  M.  Ferein  communicated  to  the 
French  Academy  of  Sciences  a very  ingenious 
theory  on  the  formation  of  the  voice.  He  con- 
fidered  the  organ  of  the  voice  as  a Jlring^  as  well 
as  a 'wtnd^  inftrument;  fo  that  what  art  has  hi- 
therto been  unable  to  conftrud;,  and  what  both 
the  fathers  Merfenne  and  Kircher  fo  much  wifti- 
ed  to  fee,  M.  Ferein  imagined  he  had  at  length 
difcovered  in  the  human  body.  He  cjbferves, 
that  there  are  at  the  edges  of  the  glottis  certain 
tendinous  chords,  placed  horizontally  acrofs  it, 
which  are  capable  of  confiderable  vibration,  fo 
as  to  produce  found,  in  the  fame  manner  as  it  is 
produced  by  the  firings  of  a violin  or  a harpfi-' 
chord : and  he  fuppofes  that  the  air,  as  it  pafles 
out  from  the  lungs,  adts  as  a bow  on  thefe  firings, 
while  the  efforts  of  the  breafl  and  lungs  regulate 
its  motion,  and  produce  the  variety  of  tones. 
So  that  according  to  this  fyflem  the  variation  in 
the  voice  is  not  occafioned  by  the  dilatation  or 
contradtion  of  the  glottis,  but  by  the  diflenfion  or 
relaxation  of  thefe  firings,  the  found  being  more 
or  lefs  acute  in  proportion  as  they  are  more  or 


Part  IV.  OF  THL  THORAX.  347 

lefs  ftretched  out.  Another  writer  on  this  fub- 
je£t  fuppofes,  that  the  organ  of  voice  is  a double 
inftrument,  which  produces  in  unifon  two  founds 
of  a different  nature ; one  by  means  of  the  air, 
and  the  other  by  means  of  the  chords  of  the 
glottis.  Neither  of  thefe  fyftems,  however,  are 
univerfally  adopted.  They  are  both  liable  to 
infuperable  difficulties  ; fo  that  the  manner  in 
which  the  voice  is  formed  has  never  yet  been  fa- 
tisfadtorily  afcertained  : we  may  obferve,  how- 
ever, that  the  found  produced  by  the  glottis  is 
not  articulated.  To  effedt  this,  it  is  required  to 
pafs  through  the  mouth,  where  it  is  differently 
modified  by  the  adtion  of  the  tongue,  which  is 
either  puffied  againft  the  teeth,  or  upwards  to- 
wards the  palate;  detaining  it  in  its  paffage,  or 
permitting  it  to  flow  freely,  by  contradling  or  di- 
lating the  mouth. 

Sect.  IX.  Of  Deje£lloft. 

By  dejedlion  we  mean  the  adt  of  voiding  the 
fseces  at  the  anus  ; and  an  account  of  the  man- 
ner in  which  this  is  condudled  was  referved  for 
this  part  of  the  work,  becaufe  it  feemed  to  re- 
quire a knowledge  of  refpiration  to  be  perfedtly 
underflood. 

The  inteftines  were  defcribed  as  having  a pe- 
riftaltic  motion,  by  which  the  faeces  were  gra- 
dually advancing  towards  the  anus.  Now,  when- 
ever the  faeces  are  accumulated  in  the  inteftinum 

redtum 


348  OF  THE  THORAX.  Part  IV. 

redlum  in  a fiifficient  quantity  to  become  trouble- 
fome,  either  by  their  weight  or  acrimony,  they 
excite  a certain  uneafmefs  which  induces  us  to 
go  to  ftool. — To  efFed:  this,  we  begin  by  mak- 
ing a confiderable  infpiration  ; in  eonfequence  of 
which  the  diaphragm  is  carried  downwards  to- 
wards the  lower  belly  ; the  abdominal  mufcles 
are  at  the  fame  time  contraded  in  obedience  to 
the  will ; and  the  inteftines  being  comprefled  on 
all  fides,  the  refiftance  of  the  fphin£ier  is  over- 
come, and  the  feces  pafs  out  at  the  anus ; which 
is  afterwards  drawn  up  by  its  longitudinal  fibres, 
which  are  called  levatores  ani^  and  then  by  means 
of  its  fphinBer  is  again  contraded  : but  it  fome- 
times  happens,  as  in  dyfenteries,  for  inftance, 
that  the  feces  are  very  liquid,  and  have  confi- 
derable acrimony ; and  then  the  irritation  they 
occafion  is  more  frequent,  fo  as  to  promote  their 
difcharge  without  any  prefliire  from  the  dia- 
phragm or  abdominal  mufcles  ; and  fometimes 
involuntarily,  as  is  the  cafe  when  the  fphinder 
becomes  paralytic. 

Sect.  X.  Of  the  Pericardium^  and  of  the  Heart 
a7id  its  Auricles. 

The  two  membranous  bags  of  the  pleura, 
which  were  deferibed  as  forming  the  mediafti- 
num,  recede  one  from  the  other,  fo  as  to  afford 
a lodgement  to  a firm  membranous  fac,  in  which 
the  heart  is  fecurely  lodged ; this  fac,  which  is 

the 


Part  IV.  OF  THE  THORAX.  349 

the  pericardium^  appears  to  be  compofed  of  two 
tunics,  united  to  each  other  by  cellular  mem- 
brane.— The  outer  coat,  which  is  thick,  and  in 
fome  places  of  tendinous  complexion,  is  a pro- 
duction of  the  mediaftinum ; the  inner  coat, 
which  is  extremely  thin,  is  reflected  over  the 
auricles  and  ventricles  of  the  heart,  in  the  fame 
manner  as  the  tunica  conjunCtiva,  after  lining  the 
eye  lids,  is  reflected  over  the  eye. 

This  bag  adheres  to  the  tendinous  part  of 
the  diaphragm,  and  contains  a coagulable  lymph, 
the  liquor  pericardii^  which  ferves  to  lubricate 
the  heart  and  facilitate  its  motions ; and  feems  to 
be  fecreted  and  abforbed  in  the  fame  manner  as 
it  is  in  the  other  cavities  of  the  body. 

The  arteries  of  the  pericardium  are  derived 
from  the  phrenic,  and  its  veins  pafs  into  veins  of 
the  fame  name  ; its  nerves  are  likewife  branches 
of  the  phrenic. 

The  fize  of  the  pericardium  is  adapted  to  that 
of  the  heart,  being  ufually  large  enough  to  con- 
tain it  loofely.  As  its  cavity  does  not  extend  to 
the  fternum,  the  lungs  cover  it  in  infpiration ; 
and  as  it  every  where  invefts  the  heart,  it  effectu- 
ally fecures  it  from  being  injured  by  lymph,  pus, 
or  any  other  ffuid,  extravafated  into  the  cavities 
of  the  thorax. 

The  heart  is  a hollow  mufcle  of  a conical  fliape, 
fituated  tranfverfely  between  the  two  laminse  of 
the  mediaftinum,  at  the  lower  part  of  the  thorax ; 
having  its  bafis  turned  towards  the  right  fide,  and 

its 


350  OF  THE  THORAX.  Part  IV; 

its  point  or  apex  towards  the  left. — Its  lower  fuf- 
face  is  fomewhat  flattened  towards  the  diaphragm. 
Its  balls,  from  which  the  great  velTels  originate^ 
is  covered  with  fat,  and  it  has  two  hollow  and 
fielhy  appendages,  called  auricles, — Round  thefe 
feveral  openings,  the  heart  feems  to  be  of  a firm 
ligamentous  texture,  from  which  all  its  fibres 
feem  to  originate ; and  as  they  advance  from 
thence  tovsrards  the  apex,  the  fubftance  of  the 
heart  feems  to  become  thinner. 

The  heart  includes  twm  cavities  or  ventricles,, 
which  are  feparated  from  each  other  by  a flelhy 
feptum  ; one  of  thefe  is  called  the  right  and  the 
other  the  left,,  ventricle  ; though  perhaps,  with 
refpeftto  their  fituation,  it  would  be  more  pro-i 
per  to  diftingi^ilh  them  into  the  anterior  and  pof- 
tCrior  ventricles. 

The  heart  is  exteriorly  covered  by  a very  fine 
membrane  ; and  its  ftruilure  is  perfectly  mufcu- 
lar  or  fleiliy,  being  compofed  of  fibres  which 
are  defcribed  as  palling  in  different  directions  ; 
fome  as  being  extended  longitudinally  from  the 
bafis  to  the  apex  ; others,  as  taking  an  oblique  or 
fpiral  courfe;  and  a third  fort  as  being  placed  in 
a tranfverfe  direction  (a).— -Within  the  two 
ventricles  we  obferve  feveral  furrows ; and  there 

are 

(a)  Authors  dlfFer  about  the  courfe  and  diftlndtlons  of 
thefe  fibres ; and  it  feems  right  to  obferve,  that  the  fcru^fiire 
of  the  heart  being  more  compaft  titan  that  of  ether  mufdes> 
its  fibres  are  not  eafiiy  feparated. 


Part  IV.  OF  THE  THORAX.  351 

are  likewife  tendinous  firings,  which  arlfe  from 
columna  in  the  two  cavities,  and  are  attach- 
ed to  the  valves  of  the  auricles  ; That  the  ufe  of 
thefe  and  the  other  valves  of  the  heart  may  be 
underflood,  it  mull  be  obferved,  that  four  large 
veffels  pafs  out  from  the  bafis  of  the  heart,  viz. 
two  arteries  and  two  veins ; and  that  each  of 
thefe  veffels  is  furnifhed  with  a thin  membran- 
ous production,  which  is  attached  all  round  to 
the  borders  of  their  feveral  orifices,  from  whence 
hanging  loofely  down  they  appear  to  be  divided 
into  two  or  three  diflinCt  portions.  But  as  their 
ufes  in  the  arteries  and  veins  are  different,  fo  are 
they  differently  difpofed.  Thbfe  of  the  arteries 
are  intended  to  give  way  to  the  paffage  of  the 
blood  into  them  from  the  ventricles,  but  to  op- 
pofe  its  return  : and,  on  the  contrary,  the  valves 
of  the  veins  are  conflruded  fo  as  to  allow  the 
blood  only  to  pafs  into  the  heart.  In  confequence 
of  thefe  different  ufes,  we  find  the  valves  of  the 
pulmonary  artery  and  of  the  aorta  attached  to 
the  orifices  of  thofe  veffels,  fb  as  to  have  their 
concave  furfaces  turned  towards  the  artery ; and 
their  convex  furfaces,  which  mutually  meet  to- 
gether, being  placed  towards  the  ventricle,  only 
permit  the  blood  to  pafs  one  way,  which  is  into 
the  arteries.  There  are  ufually  three  of  thefe 
valves  belonging  to  the  pulmonary  artery,  and 
as  many  to  the  aorta  ; and  from  their  figure  they 
are  called  valvula  femilunares.  The  communi- 
cation between  the  two  great  veins  and  the  ven- 
tricles 


352  OF  THE  THORAX.  Part  IV. 

tricles  is  by  means  of  the  two  appendages  or  au- 
ricles into  which  the  blood  is  difcharged  ; fo  that 
the  other  valves  which  may  be  faid  to  belong  to 
the  veins,  are  placed  in  each  ventricle,  where 
the  auricle  opens  into  it.  The  valves  in  the 
right  ventricle  are  ufually  three  in  number,  and 
are  named  valvula  tricufpides ; but  in  the  left 
ventricle  we  commonly  obferve  only  two,  and 
thefe  arc  the  valvida  mitrales.  The  membranes 
which  form  thefe  valves  in  each  cavity  are  at- 
tached fo  as  to  project  fomewhat  forward  ; and 
both  the  tricufpides  and  the  mitrales  are  conne<ft- 
ed  with  the  tendjnous  ftrings,  which  were  de- 
fcribed  as  arifmg  from  the  flefhy  coliimnee.  By 
the  contraction  of  either  ventricle,  the  blood  is 
driven  into  the  artery  which  communicates  with 
that  ventricle;  and  thefe  tendinous  ftrings  being 
gradually  relaxed  as  the  fides  of  the  cavity  arc 
brought  nearer  to  each  other,  the  valves  natu- 
rally clofe  the  opening  into  the  auricle,  and  the 
blood  necefl'arily  directs  its  courfe  into  the  then 
only  open  paflage,  which  is  into  the  artery ; but 
after  this  contraction,  the  heart  becomes  relaxed, 
the  tendinous  ftrings  are  again  ftretched  out,  and, 
drawing  the  valves  of  the  auricle  downwards, 
the  blood  is  poured  by  the  veins  into  the  ventri- 
cle, from  whence,  by  another  contraction,  it  is 
again  thrown  into  the  artery,  as  will  be  defcrib- 
ed  hereafter.  The  right  ventricle  is  not  quite  fo 
long,  though  fomewhat  larger,  than  the  left ; 
but  the  latter  has  more  fubftance  than  the  other : 
3 and 


Part  IV.  OF  THE  THORAlC.  353 

and  this  feems  to  be,  becaufe  it  is  intended  to 
tranfmit  the  blood  to  the  moft  diftant  parts  of  the 
body,  whereas  the  right  ventricle  diftributes  it 
only  to  the  lungs. 

The  heart  receives  its  nerves  from  the  par  va- 
gum  and  the  intercoftals.  The  arteries  which 
ferve  for  its  nourifhment  are  two  in  number,  and 
arife  from  the  aorta.  They  furround  in  fome 
meafure  the  bafis  of  the  heart,  and  from  this 
courfe  are  called  the  coronary  arteries.  From 
thefe  arteries  the  blood  is  returned  by  veins  of 
the  fame  name  into  the  auricles,  and  even  into  the 
Ventricles. 

The  mufcular  bags  called  the  auricles  are  fitu- 
ated  at  the  bafis  of  the  heart,  at  the  fides  of  each 
oth^r ; and,  correfponding  with  the  two  ventri- 
cles, are  like  thofe  two  cavities  diftinguiflied  in- 
to right  and  left.  Thefe  facs,  which  are  inte- 
riorly unequal,  have  externally  a jagged  appen- 
dix ; which,  from  its  having  been  compared  to 
th€  extremity  of  an  ear,  has  given  them  their 
name  of  auricles. 

Sect.  XL  Angiology,  or  a Defcription  of  the 
Blood-vefels. 

The  heart  has  been  defcribed  as  contracting 
kfelf,  and  throwing  the  blood  from  its  two 
ventricles  into  the  pulmonary  artery  and  the 
aorta,  and  then  as  relaxing  itfelf  and  receiv- 
ing a frefh  fupply  from  two  large  veins,  which 

Z arc 


354  OF  TOE  THORAX.  Part  IV. 

are  the  pulmonary  vein  and  the  vena  cava.  We 
will  now  point  out  the  principal  diftributions  of 
thefe  veffels. 

The  pulmonary  artery  arifes  from  the  right 
ventricle  by  a large  trunk,  which  foon  divides 
into  two  confiderable  branches,  which  pafs  to 
the  right  and  left  lobes  of  the  lungs : each  of 
thefe  branches  is  afterwards  divided  and  fubdi- 
vided  into  an  infinite  number  of  branches  and 
ramifications,  which  extend  through  the  whole 
fubftance  of  the  lungs  ; and  from  thefe  branches 
the  blood  is  returned  by  the  veins,  which,  con- 
trary to  the  courfe  of  the  arteries,  begin  by  very 
minute  canals,  and  gradually  become  larger, 
forming  at  length  four  large  trunks  called  pul- 
sno?iary  veins ^ which  terminate  in  the  left  auricle 
by  one  common  opening,  from  whence  the 
blood  palfes  into  the  left  ventricle.  From  this 
fame  ventricle  arifes  the  aorta  or  great  artery,^ 
which  at  its  beginning  is  nearly  an  inch  in  dia- 
meter : it  foon  fends  off  two  branches,  the  coro- 
naries^ which  go  to  be  diftributed  to  the  heart 
and  its  auricles.  After  this,  at  or  about  the  third 
or  fourth  vertebra  of  the  back,  it  makes  a con- 
fiderable curvature  j from  this  curvature  (b)  arife 

three 

(b)  Anatomifts  ufually  call  the  upper  part  of  this  curva- 
ture aorta  afcendens  j and  the  other  part  of  the  artery  to  its 
divifion  at  the  iliacs,  aorta  defcendens  : but  they  differ  about 
the  place  where  this  diflinftion  is  to  be  introduced  j and  it 
feems  fufficiently  to  anfwer  every  purpofe,  to  {peak  only  of 
lire  aorta  and  its  curvature. 


Part  IV.  OF  THE  THORAX.  355 

three  arteries ; one  of  which  foon  divides  into 
two  branches.  The  firft  two  are  the  left  fub- 
clavian  and  the  left  carotid,  and  the  third  is  a 
common  trunk  to  the  right  fubclavian  and  right 
carotid ; though  fometimes  both  the  carotids 
arife  diftindlly  from  the  ac#k. 

Thefe  two  carotids  afcend  within  the  fubcla- 
vians,  along  the  fides  of  the  trachea  ; and  when 
they  have  reached  the  larynx,  divide  into  two 
principal  branches,  the  internal  and  extern4l  ca- 
rotid. The  lirft  of  thefe  runs  a little  way  back- 
wards in  a bending  dire6:ion  ; and  having  reach- 
ed the  under  part  of  the  ear,  palTes  through  the 
canal  into  the  os  petrofum,  and  entering  into  the 
cavity  of  the  cranium,  is  diftributed  to  the  brain 
and  the  membranes  which  invelope  it,  and  like- 
wife  to  the  eye.  The  external  carotid  divides 
intofeveral  branches,  which  are  diftributed  to 
the  larynx,  pharynx,  and  other  parts  of  the 
neck ; and  to  the  jaws,  lips,  tongue,  eyes, 
temples  ; and  all  the  external  parts  of  the  head. 

Each  fubclavian  is  likewife  divided  injto  a 
great  number  of  branches.  It  fends  off  the  ver- 
tebral artery.,  which  pafles  through  the  openings 
we  fee  at  the  bottom  of  the  tranfverfe  procefles 
of  the  vertebras  of  the  neck,  and  in  its  courfe 
fends  off  many  ramifications  to  the  neighbour- 
ing parts.  Some  of  its  branches  are  diftributed 
to  the  fpinal  marrow,  and  after  a confiderable 
inflexion  it  enters  into  the  cranium,  and  is  dif- 
tributed to  the  brain.  The  fubclavian  likewife 

Z 2 fends 


35(5  OF  THE  THORAX.  Part  IV. 

fends  off  branches  to  the  mufcles  of  the  neck 
and  the  fcapula  ;and  mediaftinum,  thymus,  peri- 
cardium, diaphragm,  the  breafts,  and  the  muf- 
cles of  the  thorax,  and  even  of  the  abdomen, 
derive  branches  from  the  fubclavian,  which  are 
diftinguilhed  by  different  names,  alluding  to  the 
parts  to  which  they  are  diftributed ; and  the 
mammary^  the  phrenic^  the  'mtercojlal^  &c.  But 
notwithftanding  the  great  number  of  branches 
which  have  been  defcribed  as  arifmg  from  the 
fubclavian,  it  is  ftill  a confiderable  artery  when 
it  reaches  the  axilla^  where  it  drops  its  former 
name,  which  alludes  to  its  paffage  under  the  cla- 
vicle. and  is  called  the  axillary  artery  ; from 
which  a variety  of  branches  are  diftributed  to  the 
mufcles  of  the  breaft,  fcapula,  and  arm. — But 
its  main  trunk  taking  the  name  of  brachialls^ 
runs  along  ou  the  infide  of  the  arm  near  the  os 
humeri,  till  it  reaches  the  joint  of  the  fore-arm, 
and  theu  it  divides  into  branches.  This  divi- 
lion  however  is  different  in  different  fubjedls  ; 
for  in,  fome  it  takes  place  higher  up  and  in  others 
lower  down.  When  it  happens  to  divide  above 
the  joint,  it  rnay  be  confidered  as  a happy  dif- 
pofition  in  caie  of  an  accident  by  bleeding  ; for 
iuppoiing  the  artery  to  be  unfortunately  punc- 
tured by  the  lancet,  and  that  the  h:emorrhage 
could  only  be  ftopped  by  making  a ligatmre  on 
the  veffel,  one  branch  would  remain  unhurt,, 
through  which  the  blood  would  pafs  uninterupt- 
ed  to  the  fore-arm  and  hand.  One  of  the  two 

branches 


Part  IV.  OF  THE  THORAX.  357 

branches  of  the  brachialls  plunges  down  under 
the  flexor  mufcles,  and  runs  along  the  edge  of 
the  ulna ; while  the  other  is  carried  along  the 
outer  furface  of  the  radius,  and  is  eafily  felt  at 
the  wrift,  where  it  is  only  covered  by  the  com- 
mon integuments.  Both  thefe  branches  comi- 
monly  unite  in  the  palm  of  the  hand,  and  form 
an  arterial  arch  from  whence  branches  are  de- 
tached to  the  fingers. 

The  aorta^  after  having  given  off*  at  its  cur- 
vature the  carotids  and  fubclavians  which  convey 
blood  to  all  the  upper  parts  of  the  body,  defcends 
upon  the  bodies  of  the  vertebras  a little  to  the  left, 
as  far  as  the  os  facrum, where  it  drops  the  nameof 
aorta^  and  divides  into  two  confiderable  branches. 
In  this  courfe,  from  its  curv’^ature  to  its  bifurca- 
tion, it  fends  off  feveral  arteries  in  the  following 
order  : i . One  or  two  little  arteries,  firfc  demon- 
ftrated  by  Ruyfch  as  going  to  the  bronchi,  and 
called  arteria  bronchinales  Ruyfch li.  2.  The  ar- 

terias  oefophageas.  Thefe  are  commonly  three 
or  four  in  number.  They  arife  from  the  fore- 
part of  the  aorta,  and  are  difiributed  chiefly  to 
the  oefophagus.  3.  The  inferior  intercoflal  ar- 
teries, which  are  difiributed  between  the  ribs  in 
the  fame  manner  as  the  arteries  of  the  three  or 
four  fuperior  ribs  are,  which  are  derived  from 
the  fiibclavian.  Thefe  arteries  fend  off  branches 
to  the  medulla  fpinalis.  4.  The  diaphragmatic 
or  inferior  phrenic  arteries,  which  go  to  the 
diaphragm,  ftomach,  omentum,  duodenum, 

pancreas 


358  OF  THE  THORAX.  Part  IV, 

pancreas,  fpleen,  liver,  and  gall-bladder.  5. 
The  cceliac,  which  fends  off  the  coronary-fto- 
machic,  the  fplenic,  and  the  hepatic  artery.  6. 
The  fuperior  mefenteric  artery  and  fmall  intef- 
tines.  7.  The  emulgents,  which  go  to  the  kid- 
neys. 8.  The  arteries,  which  are  diftributed 
to  the  glandul^E  renales.  9.  The  fpermatic. 
10.  The  inferior  mefenteric  artery,  which  ra- 
mifies through  the  lower  portions  of  the  mefen- 
tery  and  the  large  inteftines. — A branch  of  this 
artery  which  goes  to  the  reftum  is  called  the  in- 
ternal  hemorrhoidal.  1 1 . The  lumbar  arteries, 
and  a very  fmall  branch  called  the  facra.,  which 
are  diftributed  to  the  mufcles  of  the  loins  and 
abdomen,  and  to  the  os  facrum  and  medulla 
fpinalis. 

The  trunk  of  the  aorta,  when  it  has  reached 
thelaft  vertebra  lumborum,or  the  os  facrum,  drops 
the  name  of  aorta.,  and  feparates  into  two  fork- 
ed branches  called  the  iliacs.  Each  of  thefe  foon 
divides  into  two  branches  ; one  of  which  is  call- 
ed internal  iliac.,  or  hypogajlrie  artery.,  and  is  dif-i 
tributed  upon  the  contents  of  the  pelvis  and  up- 
on the  mufcles  on  its  outer  fide.  One  branch, 
called  pudenda  communis,  fends  fmall  ramifica- 
tions to  the  end  of  the  re£tum  under  the  name 
of  hcemorrhoides  cxte?ma,  and  is  afterwards  dif- 
tributed upon  the  penis.  The  other  branch,  the 
external  iliac,  after  having  given  off  the  cir- 
cumflex artery  of  the  os  ilium  and  the  epigaftric, 
which  is  diftributed  to  the  redti-mufcles,  paffes 

out 


Part  IV.  OF  THE  THORAX.  3 59 

out  of  the  abdomen  under  Poupart’s  ligament, 
and  takes  the  name  of  crural  artery,  it  de- 
fcends  on  the  inner  part  of  the  thigh  clofe  to 
the  os  femoris,  fending  off  branches  to  the  muf- 
cles,  and  then  finking  deeper  in  the  hind  part  of 
the  thigh,  reaches  the  ham,  where  it  takes  the 
name  of  popliteal : after  this  it  feparates  into  two 
conliderable  branches : one  of  which  is  called 
the  anterior  tibial  artery  ; the  other  divides  into 
two  branches,  and  thefe  arteries  all  go  to  be  dif- 
tributed  to  the  leg  and  foot. 

The  blood,  which  is  thus  diftributed  by  the 
aorta  to  all  parts  of  the  body,  is  brought  back  by 
the  veins,  which  are  fuppofed  to  be  continued 
from  the  ultimate  branches  of  arteries ; and 
uniting  together  as  they  approach  the  heart,  at 
length  from  the  large  trunks,  the  vena  cava 
afcendens,  and  vena  cava  defccndens. 

All  the  veins  which  bring  back  the  blood  from 
the  upper  extremities,  and  from  the  head  and 
breaft,  pafs  into  the  vena  cava  defcendens  ; and 
thofe  which  return  it  from  the  lower  parts  of 
the  body  terminate  in  the  vena  cava  afcendens ; 
and  thefe  two  cavas  uniting  together  as  they  ap- 
proach the  heart,  open  by  one  common  orifice 
into  the  left  auricle. 

It  does  not  here  feem  to  be  neceffary  to  fol- 
low the  different  divifions  of  the  veins  as  we  did 
thofe  of  the  arteries  ; and  it  will  be  fufficient  to 
remark,  that  in-  general  every  artery  is  accom- 
panied by  its  vein,  and  that  both  are  difliiiguiflied 

by 


360  OF  THE  THORAX.  Part  IV. 

by  the  fame  name.  But,  like  many  other  ge- 
neral rules,  this  too  has  its  exceptions  (c).  The 
veins  for  inftance,  which  accompany  the  exter- 
nal and  internal  carotid,  are  not  called  the  car- 
told  veins ^ but  the  external  and  internal  jugular, 
— In  the  thorax,  there  is  a vein  diftinguifhed 
by  a proper  name,  and  this  is  the  a%ygos^  or  ve- 
na fine  parti.  This  vein,  which  is  a pretty  con- 
fiderable  one,  runs  along  by  the  right  fide  of 
the  vertebrse  of  the  back,  and  is  chiefly  deftin- 
ed  to  receive  the  blood  from  the  intercoftals  on 
that  fide,  and  from  the  lower  half  of  thofe  on 
the  left  fide,  and  to  convey  it  into  the  vena  cava 
defcendens.  In  the  abdomen  we  meet  with  a 
vein,  which  is  ftill  a more  remarkable  one,  and 
this  is  the  vena  porta ^ which  performs  the  office 
both  of  an  artery  and  a vein.  It  is  formed  by 
a re-union  of  all  the  veins  which  come  from  the 
ftomach,  inteftines,  omentum,  pancreas,  and 
fpleen,  fo  as  to  compofe  one  great  trunk,  which 
goes  to  ramify  through  the  liver  ; and  after  hav- 
ing depofited  the  bile,  its  ramifications  unite  and 
bring  back  into  the  vena  cava,  not  only  the  blood 
which  the  vena  portse  had  carried  into  the  fiver, 
but  likewife  the  blood  from  the  hepatic  artery. 
Every  artery  has  a vein  which  correfponds  with 
it ; but  the  trunks  and  branches  of  the  veins 

are 

(c)  In  the  extremities,  fome  of  the  deep-feated  veins, 
and  all  the  fuperfidal  one,  take  a courfe  dilFerent  from 
that  of  the  arteries. 


Part  IV.  OF  THE  THORAX.  361 

are  more  numerous  than  thofe  of  the  arteries. 
— The  reafons  for  this  difpofition  are  perhaps 
more  difficult  to  be  explained  ; the  blood  in  its 
courfe  through  the  veins  is  much  farther  remov- 
ed from  the  fource  and  caufe  of  its  motion, 
which  are  in  the  heart,  than  it  was  when  in  the 
arteries ; fo  that  its  courfe  is  confequently  lefs 
rapid,  and  enough  of  it  could  not  poffibly  be 
brought  back  to  the  heart  in  the  moment  of  its 
dilatation,  to  equal  the  quantity  which  is  driven 
into  the  arteries  from  the  two  ventricles,  at  the 
time  they  contract  ; and  the  equilibrium  which 
is  fo  effential  to  the  continuance  of  life  and 
health  would  confequently  be  deftroyed,  if  the 
capacity  of  the  veins  did  not  exceed  that  of 
the  arteries,  in  the  fame  proportion  that  the  ra- 
pidity of  the  blood’s  motion  through  the  arteries 
exceeds  that  of  its  return  through  the  veins. 

A large  artery  ramifying  through  the  body, 
and  continued  to  the  minute  branches  of  veins, 
which  gradually  unite  together  to  form  a large 
trunk,  may  be  compared  to  two  trees  united  to 
each  other  at  their  tops  ; or  rather  as  having 
their  ramifications  fo  difpofed  that  the  two  trunks 
terminate  in  one  common  point ; and  if  we 
farther  fuppofe,  that  both  thefe  trunks  and  their 
branches  are  hollow,  and  that  a fluid  is  incef- 
fantly  circulated  through  them,  by  entering  into 
one  of  the  trunks  and  returning  through  the  other, 
we  {hall  be  enabled  to  conceive  how  the  blood 


IS 


362  OF  THE  THORAX.  Part  IV. 

is  circulated  through  the  veffels  of  the  human 
body. 

Every  trunk  of  an  artery,  before  it  divides, 
is  nearly  cylindrical,  or  of  equal  diameter  through 
its  whole  length,  and  fo  are  all  its  branches 
when  examined  feparately.  But  every  trunk 
feems  to  contain  lefs  blood  than  the  many 
branches  do  into  which  that  trunk  feparates ; 
and  each  of  thefe  branches  probably  contains 
lefs  blood  than  the  ramifications  do  into  which 
it  is  fubdivided:  and  it  is  the  fame  with  the 
reins  ; the  volume  of  their  feveral  ramifications, 
when  confidered  together,  being  found  to  exceed 
that  of  the  great  trunk  which  they  form  by  their 
union. 

The  return  of  the  blood  through  the  veins  to 
the  heart,  is  promoted  by  the  a<3:ion  of  the  muf- 
cles,  and  the  pulfation  of  the  arteries.  And 
this  return  is  likewife  greatly  affifted  by  the 
valves  which  are  to  be  met  with  in  the  veins, 
and  which  conftitute  one  of  the  great  diftinftions 
between  them  and  the  arteries.  Thefe  valves, 
which  are  fuppofed  to  be  formed  by  the  inner 
coat  of  the  veins,  permit  the  blood  to  flow  from 
the  extremities  towards  the  heart,  but  oppofe  its 
return.  They  are  moft  frequent  in  the  Imaller 
veins.  As  the  column  of  blood  increafes,  they 
feem  to  become  lefs  neceifary  ; and  therefore  in 
the  vena  cava  afcendens,  we  meet  with  only  one 
valve,  which  is  near  its  origin. 

The  ciiteries  are  compofed  of  feveral  tunics. 

Some 


Part  IV.  OF  THE  THORAX.  363 

Some  writers  enumerate  five  of  thefe  tunics ; 
but  perhaps  we  may  more  properly  reckon  only 
three,  viz.  the  ?iervous^  mufcular^  and  cut'icular 
coats.  The  veins  are  by  Ibme  anatomifls  de- 
fcribed  as  having  the  fame  number  of  coats  as 
arteries  ; but  as  they  do  not  feem  to  be  irrita- 
ble, we  cannot  with  propriety  fuppofe  them  to 
have  a mufcular  tunic.  We  are  aware  of  Dr. 
Verfchuir’s  * experiments  to  prove  that  the  ju- 
gular and  fome  other  veins  poii'efs  a certain  de- 
gree of  irritability ; but  it  is  certain,  that  his 
experiments,  repeated  by  others,  have  produc- 
ed a different  refult ; and  even  he  himfelf  allows, 
that  fometimes  he  was  unable  to  diftinguifh  any 
fuch  property  in  the  veins.  Both  thefe  feries  of 
veffels  are  nourifned  by  ftill  more  minute  arteries 
and  veins,  which  are  feen  creeping  over  their  coats, 
and  ramifying  through  their  whole  fubfiance, 
and  are  called  vafa  vaforuni ; they  have  likewife 
many  minute  branches  of  nerves. 

The  arteries  are  much  ftronger  than  the  veins, 
and  they  feem  to  require  this  force  to  be  enabled 
to  refill;  the  impetus  with  which  the  blood  circu- 
lates through  them,  and  to  impel  it  on  towards 
the  veins. 

When  the  heart  contrads,  it  impels  the  blood 
into  the  arteries,  and  fenfibly  diftends  them  ; 
and  thefe  veffels  again  contrad,  as  the  heart  be- 
comes relaxed  to  receive  more  blood  from  the 

auricles ; 

* Dc  Arteriarum  et  Veuarum  vi  irritabili,  410, 


364  OF  THE  THORAX.  Part  IV. 

auricles ; fo  that  the  caufe  of  the  contraction 
and  dilatation  of  the  arteries  feems  to  be  eafy 
to  be  underftood,  being  owing  in  part  to 
their  own  contraCtile  power,  and  in  part  to 
the  action  of  the  heart ; but  in  the  veins ^ the  ef- 
fects of  this  impulfe  not  being  fo  fenfibly  felt, 
and  the  veffels  themfelves  having  little  or  no  con- 
tractile power,  the  blood  feems  to  flow  in  a con- 
ftant  and  equal  ftream  : and  this,  together  with 
its  paffing  gradually  from  a fmall  channel  into  a 
larger  one,  feems  to  be  the  reafon  why  the  veins 
have  no  pulfatory  motion,  except  the  large  ones 
near  the  heart  ; and  in  thefe  it  feems  to  be  oc- 
cafioned  by  the  motion  of  the  diaphragm,  and 
by  the  regurgitation  of  the  blood  in  the  cavas. 

Sect.  XII.  Of  the  A&ion  of  the  Hearty  Auri~ 
cles^  and  Arteries. 

The  heart,  at  the  time  it  contracts,  drives 
the  blood  from  its  ventricles  into  the  arteries  ; 
and  the  arteries  being  thus  filled  and  diftended, 
are  naturally  inclined  to  contraCt  the  moment 
the  heart  begins  to  dilate,  and  ceafes  to  fupply 
them  with  blood.  Thefe  alternate  motions  of 
contraction  and  dilatation  of  the  heart  and  arte- 
ries, are  diftinguifiied  by  the  names  of  fyfole  and 
diafole.  When  the  heart  is  in  a ftate  of  con- 
traction or  fyftole,  the  arteries  are  at  that  inftant 
diftended  with  blood,  and  in  their  dialtole  ; and 

it 


Part  IV.  OF  THE  THORAX.  365 

it  is  in  this  ftate  we  feel  their  pulfatory  motion, 
which  we  call  t\iQ.pulfe.  When  the  heart  dilates, 
and  the  arteries  contract,  the  blood  is  impelled 
onwards  into  the  veins,  through  which  it  is  re- 
turned back  to  the  heart.  While  the  heart,  how- 
ever, is  in  its  fyftole,  the  blood  cannot  pafs  from 
the  veins  into  the  ventricles,  but  is  detained  in 
the  auricles,  which  are  two  refervoirs  formed 
for  this  ufe,  till  the  diaftole,  or  dilatation  of  the 
heart,  takes  place  ; and  then  the  diftended  au- 
ricles contradl,  and  drive  the  blood  into  the  ven- 
tricles : fo  that  the  auricles  have  an  alternate  fyf- 
tole and  diaftole  as  well  as  the  heart. 

Although  both  the  ventricles  of  the  heart  con- 
trad:  at  the  fame  time,  yet  the  blood  pafles  from 
one  to  the  other.  In  the  fame  moment,  for  in- 
ftance,  that  the  left  ventricle  drives  the  blood 
into  the  aorta,  the  right  ventricle  impels  it  into 
pulmonary  artery,  which  is  diftributed  through 
all  the  fubftance  of  the  lungs.  The  blood  is 
afterwards  brought  back  into  the  left  ventricle  by 
the  pulmonary  vein,  at  the  fame  time  that  the 
blood  is  returned  by  the  cavas,  into  the  right 
ventricle,  from  all  the  other  parts  of  the  body. 

This  feems  to  be  the  mode  of  adion  of  the 
heart  and  its  veflels : but  the  caufe  of  this  adion 
has,  like  all  other  intricate  and  interefting  fub- 
jeds,  been  differently  explained.  It  feems  to 
depend  on  the  ftimulus  made  on  the  different 
parts  of  the  heart  by  the  blood  itfelf,  which  by 

iu 


366  OF  THE  THORAX.  Part  IV. 

its  quantity  and  heat,  or  other  properties  (d),  is 
perhaps  capable  of  hrfl:  exciting  that  motion, 
which  is  afterwards  continued  through  life,  in- 
dependent of  the  wall,  by  a regular  return  of 
blood  to  the  auricles,  in  a quantity  proportion- 
ed to  that  which  is  thrown  into  the  arteries. 

The  heart  pofl'elles  the  vis  infita^  or  principle 
of  irritability,  in  a much  greater  degree  than  any 
other  mufcle  of  the  body.  The  pulfe  is  quicker 
in  young  than  in  old  fubjefts,  becaufe  the  former 
are  ca;t.  par.  more  irritable  than  the  latter.  Up- 
on the  fame  principle  we  may  explain,  why  the 
pulfe  is  conftantly  quicker  in  weak  than  in  ro- 
buft  perfons. 

S E c T . X I II.  Of  the  Circulation. 

After  what  has  been  obferved  of  the  ftruc-> 
ture  and  adtion  of  the  heart  and  its  auricles,  and 
iikewnfe  of  the  arteries  and  veins,  there  feem  to 
[)e  but  veiy  few  arguments  required  to  demon- 
ftrate  the  circulation  of  the  blood.^  which  has  long 
Imce  been  eftabliflied  as  a medical  truth.  This 
circulation  may  he  denned  to  be  a perpetual  mo- 
tion of  the  blood,  in  confeqtiencc  of  the  aftion 

of 

(d)  Dr.  Harvey  long  ago  fuggefled,  that  the  blood  is  pof- 
icffed  ul  a livip.g  principle  ; and  Mr.  J.  Hunter  has  lately  en- 
ileavourcd  to  rc\h  e this  do6lrine-,  in  fupport  of  which  he 
has  adduced  many  ingenious  arguments.  The  fiibjeft  is  a 
curious  one,  and  deferves  to  be  profecuted  as  an  inquiry 
which  cannot  but  be  Interefting  to  phyfiologifls. 


Part  IV.  OF  THE  THORAX.  367 

of  the  heart  and  arteries,  which  impel  it 
through  all  the  parts  of  the  body,  from  whence 
it  is  brought  back  by  the  veins  of  the  heart. 

A very  fatisfadlory  proof  of  this  circulation, 
and  a proof  eafy  to  be  underftood.  may  be  de- 
ducted from  the  different  eifeCls  of  preffure  on 
an  artery  and  a vein.  If  a ligature,  for  inftance, 
is  paffed  round  an  artery,  the  veffel  fwells  con- 
fiderably  between  the  ligature  and  the  heart ; 
whereas,  if  we  tie  up  a vein,  it  only  becomes 
filled  between  the  extremity  and  the  ligature, 
and  this  is  what  we  every  day  obferve  in  bleed- 
ing. The  ligature  we  pafs  round  the  arm  on 
thefe  occafions,  compreffes  the  fuperficial  veins; 
and  the  return  of  the  blood  through  them  be- 
ing impeded,  they  become  diflended.  When 
the  ligature  is  too  loofe,  the  veins  are  not  fuffi- 
ciently  compreffed,  and  the  blood  continues  its 
progrefs  towards  the  heart ; and,  on  the  con- 
trary, when  it  is  made  too  tight,  the  arteries 
themfefves  becomes  comprefl'ed  ; and  the  flow  of 
the  blood  through  them  being  impeded,  the 
veins  cannot  be  diflended. 

Another  phsenomenon,  which  effectually 
proves  the  circulation,  is  the  lofs  of  blood  that 
every  living  animal  fuflains  by  opening  only  a 
Angle  artery  of  a moderate  fize  ; for  it  continues 
to  flow  from  the  wounded  veffel  till  the  equili- 
brium is  deflroyed  which  is  ellential  to  life.  This 
truth  was  not  unknown  to  the  ancients  ; and  it 
feems  ftrange.  thaf*it  did  not  lead  them  to  a 

knowledge 


368  OF  THE  THORAX.  Part  IV. 

knowledge  of  the  circulation,  as  it  fufficiently 
proves,  that  all  the  other  veflels  muft  communi- 
cate with  that  which  is  opened.  Galen,  who 
lived  more  than  1500  years  ago,  drew  this  con- 
clufion  from  it ; and  if  we  farther  obferve,*  that 
he  defcribes  (after  Erafiftratus,  who  flourifhed 
about  450  years  before  him)  the  feveral  valves 
of  the  heart,  and  determines  their  difpofition 
and  ufes,  it  will  appear  wonderful,  that  a pe- 
riod of  near  200  years  fhould  afterwards  elapfe 
before  the  true  eourfe  of  the  blood  was  afcertain- 
ed.  This  difcovery,  for  which  we  are  indebt- 
ed to  the  immortal  Harvey,  has  thrown  new 
lights  on  phyfiology  and  the  dodlrine  of  dif- 
eafes,  and  conftitutes  one  of  the  moft  impor- 
tant periods  of  anatomical  hiftory. 

Sect.  XIV.  Of  the  Nature  of  the  Blood. 

Blood,  recently  drawn  from  a vein  into  a 
bafon,  would  feem  to  be  an  homogeneous  fluid 
of  a red  colour  (e)  ; but  when  fuffered  to  reft, 
it  foon  coagulates,  and  divides  into  two  parts, 
which  are  diftinguifhed  by  the  names  of  crajfa- 
vientum  and  ferum.  The  cralfamentum  is  the 
red  coagulum,  and  the  ferum  is  the  water  in 
which  it  floats.  Each  of  thefe  may  be  agmn  fe- 
parated  into  two  others ; for  the  cralfamentum, 

by 

(e)  The  blood,  as  it  flows  through  the  arteries,  is  ob- 
ferved  to  be  more  florid  than  it  is  in  the  veins  ; and  this  red- 
nefsis  acquired  in  its  paflage  through  the  lungs.  Vid.  fe£t.  vii. 


Part  IV.  OF  THE  TFIORAX.  369 

by  being  repeatedly  wafhed  in  warm  water,  gives 
out  all  its  red  globules,  and  what  remains  ap- 
pears to  be  compoled  of  the  coagulablelymph(F), 
which  is  a gelatinous  fubftance,  capable  of  being 
hardened  by  fire  till  it  becomes  perfedfly  horny : 
and  if  we  expofe  the  ferum  to  a certain  degree 
of  heat,  part  of  it  will  be'  found  to  coagulate 
like  the  white  of  an  egg,  and  there  will  remain 
a clear  and  lympid  water,  refembling  urine  both 
in  its  appearance  and  fmell. 

The  ferum  and  craffamentum  differ  in  their 
proportion  in  different  conftitutions  ; in  a flrong 
perfon,  the  craffamentum  is  in  a greater  pro- 
portion to  the  ferum  than  in  a weak  one  and 
the  fame  difference-is  found  to  take  place  in  dif- 
eafes  (g). 

A a Sect.  XV. 

(f)  It  may  not  be  Improper  to  obferve,  that  till  of  late  the 
c oagalable lymph  hiishttn  confounded  with  they^rw??  of  the 
blood,  which  contains  a fubftance  that  is  likewife  coagula- 
ble,  though  only  when  expofed  to  heat,  or  combined  with 
certain  chemical  fubftances ; whereas  the  other  coagulates 
fpontaneoufty  when  expofed  to  the  air  or  to  reft. 

* Hewfon’s  Experinj.  Enq.  Part.  I. 

(g)  When  the  blood  feparates  into  ferum  and  crajfaine?i- 
tum,  if  the  latter  be  covered  with  a cruft  of  a whitifti  or 
buff  colour,  it  has  been  ufually  confidered  as  a certain 
proof  of  the  blood’s  being  in  a ftate  of  too  great  vilddity. 
This  appearance  commonly  taking  place  in  inflammatory 
difeales,  has  longferved  to  confirm  the  theory  which  afcribes 
the  caufe  of  inflammation  to  lentor  and  obftrudtions.  But 
from  thq  late  Mr.  Hewfon’s  experiments  it  appears,  that 
when  the  adlion  of  the  arteries  is  increafed,  the  blood,  in- 
ftead  of  being  more  vifcid,  is,  on  the  conrtary,  more  fluid 

than 


370  OF  THE  THORAX.  Part  IV. 

Sect.  XV.  Of  Nutrition. 

The  variety  of  functions  which  we  have  de- 
fcribed  as  being  inceflantly  performed  by  the  liv- 
ing body,  and  the  continual  circulation  of  the 
blood  'through  it,  mult  neceffarily  occafion  a 
conftant  diflipation  of  the  feveral  parts  which 
enter  into  its  cornpofition.  In  fpeaking  of  the 
infenfible  perfpiration,  we  obferved  how  much 
was  inceflantly  -pafling  off  from  the  lungs  and 
the  flirfao'e  of  the  fkin.  The  difcharge  by  urine 
is  likewife  every  day  confiderable  ; and  great 
part  of  the  bile,  faliva,  &c.  are  excluded  by 
ftool.  But  the  folid,  as  well  as  the  fluid  ipatts 
of  the  body,  require  a conftant  renewal  of  nu- 
tritious :particles.  They  are  expofed  to  the  at- 
trition of  the  fluids  w'^hich  are  circulated  through 
them  ; and  the  contraction  and  relaxation  they 
repeat  fo  many  thoufand  times  in  every  day, 
would  neccflTarily  occafion  a diflolution  of  the 
machine,  if  the  renewal  was  not  proportioned 
to  the  wafte. 

It  is  eafy  to  conceive  how  the  chyle  Formed 
from  the  aliment  is  aflimilated  into  the  nature  of 

the 

fhaninthe  ordinary  ftate,  previous  to  Inflammation:  and 
that  in  conlequence  of  this,  the  coa:gulaSle  lymph  fuffers 
the  red  globules,  which  are  the  heavieft  part  of  the  blood, 
to  fall  down  to  the  bottom  before  it  coagulates : fo  that 
the  dra'flamentum  is  divided  into  two  parts ; one  of  which 
is  found  to  confifl:  of  the  coagulable  lymph  alone  (in  this  cafe 
termed  the  and  the  other,  partly. of  this  and  paitly 

of  the  red  globules^ 


Part  IV.  OF  THE  TEIORAX.  371 

the  blood,  and  repairs  the  lofs  of  the  fluid  parts 
of  our  body  ; but  how  the  folids  are  renewed, 
has  never  yet  been  fatisfadloriiy  explained.  The 
nutritious  parts  of  the  blood  are  probably  de- 
pofited  by  the  arteries  by  exfudation  through 
their  pores  into  the  tela  cellulofa  ; and  as  the 
folid  parts  of  the  body  are  in  the  embryo  only 
a kind  of  jelly,  which  gradually  acquires  the 
degree  of  confiftence  they  are  found  to  have 
when  the  body  arrives  at  a more  advanced  age  ; 
and  thefe  fame  parts  which  confift  of  bones, 
cartilages,  ligaments,  mufcles,  &c.  are  fome- 
times  reduced  again  by  difeafes  to  a gelati- 
nous ftate  ; we  may,  with  fome  degree  of  pro- 
bability, confider  the  coagulable  lymph  as  the 
fource  of  nutrition. 

If  the  fupply  of  nourilhment  exceeds  the  de- 
gree of  wafte,  the  body  increafes  ; and  this  hap- 
pens in  infancy  and  in  youth  : for  at  thofe  peri- 
ods, but  more  particularly  the  former  one,  the 
fluids  bear  a large  proportion  to  the  folids  ; and 
the  fibres  being  foft  and  yielding,  are  proporti- 
onably  more  capable  of  extenfion  and  increafe. 
But  when  the  fupply  of  nutrition  only  equals 
the  wafte,  we  neither  increafe  or  decreafe  ; and 
we  find  this  to  be  the  cafe  when  the  body  has 
attained  its  full  growth  or  acme : for  the  folids 
having  then  acquired  a certain  degree  of  firm- 
nefs  and  rigidity  do  not  permit  a farther  in- 
creafe of  the  body.  But  as  we  approach  to  old 
age,  rigidity  begins  to  be  in  excefs,  and  the 

A a 2 fluids 


572  OF  THE  THORAX.  Part  IV. 

fluids  (h)  bear  a much  lefs  proportion  to  thefo- 
iids  than  before.  The  diffipation  of  the  body 
is  greater  than  the  fupply  of  nourifhment ; many 
of  'the  fmailer  veflels  become  gradually  imper- 
vious (i)  ; and  the  fibres  lofing  their  moifture 
and  their  elafticity,  appear  flaccid  and  wrinkled. 
The  lilies  and  the  rofes  difappear,becaufe  the  fluids 
by  which  they  were  produced  can  no  longer  reach 
the  extremities  of  the  capillary  veflels  of  the  Ikin. 
As  thefe  changes  take  place,  the  nervous  power 
being  proportionably  weakened,  the  irritability 
and  fenfibility  of  the  body,  which  were  formerly 
fo  remarkable,  are  greatly  diminifhed  ; and  in 
advanced  life,  the  hearing,  the  eye-fight,  and 
all  the  other  fenfes,  become  gradually  impaired. 

Sect.  XVI.  Of  the  Glands  and  Secretions. 

The  glands  are  commonly  underftood  to  be 
finall,  roundifh,  or  oval  bodies  formed  by  the 
convolution  of  a great  number  of  veflels,  and 
deftined  to  feparate  particular  humours  from  the 
mafs  of  blood. 

They  are  ufually  divided  into  two  clafles ; but 

it 

(h)  As  the  fluids  become  lels  in  proportion  to  the  folids, 
their  acrimony  is  found  to  increafe ; and  this  may  perhaps 
compenfate  for  the  want  of  fluidity  in  the  blood,  by  dimi- 
nilhing  its  cohefion. 

(i)  In  infancy,  the  arteries  are  numerous  and  large  in 
refpeft  to  the  veins,  and  the  lymphatic  glands  are  larger 
than  at  any  other  time  of  life ; whereas,  in  aid  age,  the  ca- 
pacity of  the  venous  fyftem  exceeds  that  of  the  arteries,  and 
the  lymphatic  fyftem  almoft  difappears. 


Part  IV.  OF  THE  THORAX.  373 

it  feems  more  proper  to  diftinguifh  three  kinds 
of  glands,  viz.  the  mucous,  conglobate,  and  con- 
glomerate. 

The  mucous  glands^  or  follicles,  as  they  are  moft 
commonly  called,  are  fmall  cylindrical  tubes 
continued  from  the  ends  of  arteries.  In  fome 
parts  of  the  body,  as  in  the  tonfils,  for  example, 
feveral  of  thefe  follicles  may  be  feen  folded  to- 
gether in  one  common  covering,  and  opening 
into  one  common  iinus.  Thefe  follicles  are  the 
velfels  that  fecrete  and  pour  out  mucus  in  the 
mouth,  oefophagus,  ftomach,  intefdnes,  and  other 
parts  of  the  body. 

The  conglobate  glands  are  peculiar  to  the  lym- 
phatic fyftem.  Every  lymphatic  vein  paffes 
through  a gland  of  this  kind  in  its  way  to  the 
thoracic  duft.  They  are  met  with  in  different 
parts  of  the  body,  particularly  in  the  axilla,  groin, 
and  mefenteiy , and  are  either  folitary  or  in  diftindf 
duffers. 

The  conglomerate  glands  are  of  much  greater 
bulk  than  the  conglobate,  and  feem  to  be  an  af- 
lemblage  of  many  fmaller  glands.  Of  this  kind 
are  the  liver,  kidneys,  &e.  Some  of  them,  as 
the  pancreas,  parotids,  &c.  have  a granulated  ap- 
pearance. All  thefe  conglomerate  glands  are 
plentifully  fupplied  with  blood-veffels  ; but  their 
nerves  are  in  general  very  minute,  and  few  in 
number.  Each  little  granulated  portion  fur- 
niflies  a fmall  tube,  which  unites  with  other  fi- 

milar 


374  OF  the  thorax.  Part  IV. 

milar  ducSls,  to  form  the  common  excretory  du£t 
of  the  gland. 

The  principal  glands,  and  the  humours  they 
fecrete,  have  been  already  defcribed  in  different 
parts  of  this  work ; and  there  only  remains  for 
us  to  examine  the  general  ftru£ture  of  the  glands, 
and  to  explain  the  mechanifm  of  fecretion.  On 
thefirftof  thefe  fubjedts  two  different  fyftems 
have  been  formed  ; each  of  which  has  had,  and 
fall  continues  to  have,  its  adherents.  One  of 
thefe  fyftems  was  advanced  by  Malpighi,  who 
fuppofed  that  an  artery  entering  into  a gland  ra- 
mifies very  minutely  through  its  whole  fubftance ; 
and  that  its  branches  ultimately  terminate  in  a 
veficular  cavity  or  follicle,  from  whence  the  fe- 
creted  fluid  paffes  out  through  the  excretory  dudf. 
This  dodtrine  at  firft  met  with  few  opponents ; 
but  the  celebrated  Ruyfch,  who  firft  attempted 
minute  injedtions  with  wax,  afterwards  difputed 
the  exiftence  of  thefe  follicles,  and  afferted,  that 
every  gland  appears  to  be  a continued  feries  of 
veffels,  which  after  being  repeatedly  convoluted 
in  their  courfe  through  its  fubftance,  at  length 
terminate  in  the  excretory  dudt.  Anatomifts 
are  ftill  divided  between  thefe  two  fyftems  : that 
of  Malpighi,  however,  feems  to  be  the  beft 
founded,  ^ , 

The  mode  of  fecretion  has  been  explained  in 
a variety  of  ways,  and  they  are  all  perfedlly  hy- 
pothetical. In  fuch  an  inquiiy  it  is  natural  to 
afle,  how  one  gland  conftantly  feparates  a parti- 
cular 


Part  IV.  OF  THE  THORAX.  37 5 

cular  humour,  while  another  gland  fecretes  one 
of  a very  different  nature  from  the  blood  ? The 
bile,  for  infta.nce,  is  feparated  by  the  liver,  and 
the  urine  by  the  kidneys.  Are  thefe  fecretions 
to  be  imputed  to  any  particular  difpofitions  in 
the  fluids,  or  is  their  caufe  to  be  looked  for  in 
the  folids  ? 

It  has  been  fuppofed,  that  every  gland  con- 
tains within  itfeif  a fermenting  principle,  by 
which  it  is  enabled  to  change  the  nature  of  the 
blood  it  receives,  and  to  endue  it  with  a particu- 
lar property.  So  that,  according  to  this  fyftem, 
the  blood,  as  it  circulates  through  the  kidneys, 
becomes  mixed  with  the  fermenting  principle  of 
thofe  glands,  and  a part  of  it  is  converted  hito 
urine  ; and  again,  in  the  liver,  in  the  faliyal  and 
other  glands,  the  bile,  tire  faliva,  and  other 
juices,  are  generated  from  a fimilar  caufe.  But 
it  feems  to  be  impoffible  for  any  liquor  to  be  con- 
fined in  a place  expofed  to  the  circulation,  with- 
out being  carried  away  by  the  ton'ent  of  blood, 
every  part  of  which  would  be  equally  affefted ; 
and  this  fyftem  of  fermentation  has  long  been 
rejected  as  vague  and  chimerical.  But  as  the 
caufe  of  fecretion  continued  to  be  looked  for  in 
the  fluids,  the  former  fyftem  was  fucceeded  by 
another,  in  which  recourfe  was  had  to  the  ana- 
logy of  the  humours.  It  was  obferved,  that  if 
paper  is  moiftened  with  water,  and  oil  and  wa- 
ter are  afterwards  poured  upon  it,  that  the  water 
only  will  be  permitted  to  pafs  through  it ; but 

that, 


376  OF  THE  THORAX.  Part  IV. 

that,  on  the  other  hand,  if  the  paper  has  been 
previoufly  foaked  in  oil  inftead  of  water,  the  oil 
only,  and  not  the  water,  will  be  filtered  through 
it.  Thefe  obfervations  led  to  a fuppofition,  that 
every  fecretory  organ  is  originally  furnilhed  with 
a humour  analogous  to  that  w^hich  it  is  after- 
wards deftined  to  feparate  from  the  blood ; aiid 
that  in  confequence  of  this  difpofition,  tl)e  fecre- 
tory vefiels  of  the  liver,  for  inftance,  will  only 
admit  the  bilous  particles  of  the  blood,  while  all 
the  other  humours  will  be  excluded.  This  fyf- 
tem  is  an  ingenious  one,  but  the  difficulties  with 
which  it  abounds  are  unanfwerable  ; for  oil  and 
water  are  immifcible  ; whereas  the  blood,  as  it 
is  circulated  through  the  body,  appears  to  be  an 
homogeneous  fluid.  Every  oil  will  pafs  through 
a paper  moiftened  only  with  one  kind  of  oil  ; 
and  wine,  or  fpirits  mixed  with  water,  will  eafily 
be  filtered  through  a paper  previoufly  foaked  in 
water.  Upon  the  fame  principle,  all  our  humours, 
though  differing  in  their  other  properties,  yet 
agreeing  in  that  of  being  perfectly  mifcible  with 
eachother,willalleafilypafsthroughthefamefiltre. 
But  thefe  are  not  all  the  objedlions  to  this  fyftem. 
The  humours  which  are  fuppofed  to  be  placed  in 
the  fecretory  velfels  for  the  determination  of  fimi- 
lar  particles  of  the  blood,  muff  be  originally  fe- 
parated  without  any  analogous  fluid  ; and  that 
which  happens  once,  may  as  eafily  happen  al- 
ways. Again,  it  fometimes  happens  from  a vi- 
cious difpofition,  that  humours  are  filtered 
through  glands  which  are  naturally  not  intended 

to 


Part  IV.  OF  THE  THORAX.  377 

to  afford  them  a paffage ; and  when  this  once 
has  happened,  it  ought,  according  to  this  fyftem, 
to  be  expected  always  to  do  fo  : whereas  this  is 
not  the  cafe  ; and  we  are,  after  all,  naturally  led 
to  feek  for  the  caufe  of  fecretions  in  the  folids. 
It  does  not  feem  right  to  afcribe  it  to  any  parti- 
cular figure  of  the  excretory  veffels  ; becaufe  the 
foft  texture  of  thofe  parts  does  not  permit  them 
to  preferve  any  conftant  fhape,  and  our  fluids 
feem  to  be  capable  of  accommodating  themfelves 
to  every  kind  of  figure.  Some  have  imputed 
it  to  the  difference  of  diameter  in  the  orifices  of 
the  different  fecretoiy  veffels.  To  this  doctrine 
objediions  have  likewife  been  railed  ; and  it  has 
been  argued,  that  the  veffels  of  the  liver,  for  in- 
ftance,  would,  upon  this  principle,  afford  a paf- 
fage not  only  to  the  bile,  but  to  all  the  other  hu- 
mours of  lefs  confiftence  with  it.  In  reply  to 
this  objediiion,  it  has  been  fuppofed,  that  fecon- 
dary  veffels  exift,  which  originate  from  the  firft, 
and  permit  all  the  humours  thinner  than  the  bile 
to  pafs  through  them. 

Each  of  thefe  hypothefes  is  probably  very  re- 
mote from  the  truth. 

EXPLANATION  of  PLATE  XXVIII. 

This  plate  reprefents  the  Heart  in  fitu,  all 
the  large  Arteries  and  Veins,  with  fome  of  the 
Mufcles,  &c. 

Muscles,  &c. — Superior  Extremity. — 
a,  Maffeter.  b,  Complexus.  C,  Digaftricus. 

d,  Os 


378  OF  THE  THORAX.  Part  IV. 

d,  Os  hyoides.  e,  Thyroid  gland,  f,  Levator 
fcapulaj.  g,  Cucullaris.  h h,  The  clavicles  cut. 
i,  The  deltoid  mufcle.  k,  Biceps  flexor  cubiti 
cut.  I,  Caraco-brachialis.  m,  Triceps,  exten-* 
for  cubiti.  n,  The  heads  of  the  pronator  teres^ 
flexor  carpi  radiales,  and  flexor  digitorum  ful> 
limis,  cut.  o,  The  flexor  carpi  ulnaris^  cut  at. 
its  exteremity.  p,  Flexor  digitorum  profundus. 

q,  Supinator  radii  longus,  cut  at  its  extremity. 

r,  Ligamentum  carpi  tranfverfale.  s,  Extenfores 
carpi  radiales.  t,  Latiffimus  dorfi.  u,  Anterior 
edge  of  the  ferratus  anticus  major,  v v,  The  in- 
ferior part  of  the  diaphragm,  w w,  Its  anterior 
edge  cut.  x x,  The  kidneys,  y,  Tranfverfus 
abdominis,  z,  Os  ilium. 

Inferior  Extremity. — Pfoas  magnus. 

Iliacus  intemus.  r,  The  flefhy  origin  of  the 
tenfor  vagina  femoris.  d The  olfa  pubis  cut 
from  each  other,  Mufculus  pe£lineus  cut 
from  its  origin,  Short  head  of  the  triceps  ab- 
ductor femoris  cut.  The  great  head  of  the 
triceps,  The  long  head  cut.  z,  Vaftus  in- 
turnus.  Vaftus  externus.  /,  Crureus. 
Gemellus.  Soleus.  o,  Tibia,  Peronaeus 
longus.  y,  Peronaeus  brevis,  r,  Fibula. 

Heart  and  Blood-vessels. — A,  The  heart, 
with  the  coronary  arteries  and  veins.  B,  The 
right  auricle  of  the  heart.  C,  The  aorta  afcen- 
dens.  D,  The  left  fubclavian  artery.  E,  The 
left  carotid  artery.  F,  The  common  trunk  which 
fends  off  the  right  fubclavian  and  right  carotid 

arteries, 


cPhiUf 


i 


Part  IV.  OF  THE  THORAX,  379 

arteries.  G,  The  carotis  externa.  H,  Arteria 
facialis,  which  lends  olF  the  coronary  arteries  of 
the  lips.  I.  Arteria  temporalis  profunda.  K, 
Aorta  defcendens.  L L,  The  iliac  arteries, — 
which  fend  off  M M,  The  femoral  or  crural  ar- 
teries. N.  B.  The  other  arteries  in  this  figure 
have  the  fame  diftribution  as  the  veins  of  the 
fame  name  : — And  generally,  in  the  anatomi- 
cal plates,  the  defcription  to  be  found  on  the  one 
fide,  points  out  the  fame  parts  in  the  other,  i , 
The  frontal  vein.  2,  The  facial  vein.  3,  Vena 
temporalis  profunda.  4,  Vena  occipitalis.  5, 
Vena  jugularis  externa.  6,  Vena  jugularis  in- 
terna, covering  the  arteria  carotis  communis.  7, 
The  vafcular  arch  on  the  palm  of  the  hand,  which 
is  formed  by,  8,  The  radial  artery  and  vein,  and, 
9,  The  ulnar  artery  and  vein.  10  10,  Cephalic 
vein.  II,  Balilic  vein,  that  on  the  right  fide 
cut.  12,  Median  vein.  13,  Tlie  humeral  vein, 
wdiich,  with  the  median,  covers  the  humeral  ar- 
tery. 14  14,  The  external  thoracic  or  mam- 
mar^"  arteries  and  veins.  15,  The  axillary  vein, 
covering  the  artery.  16  16,  The  fubclavian 
veins,  which,  with  (6  6)  the  jugulars,  form,  17, 
The  vena  cava  fuperior.  18,  The  cutaneous 
arch  of  veins  on  the  fore  part  of  the  foot.  1 9, 
The  vena  tibialis  antica,  covering  the  arterj^  20, 
The  vena  profunda  femcris,  covering  the  artery? 

21,  The  upper  part  of  the  vena  faphena  major. 

22,  The  femoral  vein.  23  23,  The  iliac  veins. 

24  24,  Vena  cava  inferior.  25  25,  The  renal 
veins  covering  the  arteries.  26  26,  The  dia- 
phragmatic veins.  PART  V. 


OF  THE  BRAIN 


Part  V. 


PART  V. 

Of  the  brain  and  NERVES, 

Sect.  I.  Of  the  Brain  and  its  Integuments. 
HE  bones  of  the  cranium  were  defcribed 


in  the  ofteological  part  of  this  work,  as  in- 


clofmg  the  brain,  and  defending  it  from  external 
injury  : but  they  are  not  its  only  protection ; for 
when  we  make  an  horizontal  feClion  through 
thefe  bones,  we  find  this  mafs  every  where  fur- 
rounded  by  two  membranes  (k),  the  dura  and 
pia  mater. — The  firft  of  thefe  lines  the  interior 
furface  of  the  cranium,  to  which  it  every  where 
adheres  ftrongly  (l),  but  more  particularly  at  the 
futures,  and  at  the  many  foramina  through  which 
veflels  pafs  between  it  and  the  pericranium.  The 


(k)  The  Greeks  called  thefe  membranes  meninges  \ but 
the  Arabians,  fuppofing  them  to  be  the  fource  of  all  the 
other  membranes  of  the  body,  afterwards  gave  them  the 
names  of  dura  and  pia  mater ; by  which  they  are  now  ufu- 
ally  diftinguiflied. 

(l)  In  young  fubjecfs  this  adhefion  is  greater  than  in 
adults  ; but  even  then,  in  the  healthy  fubjeft,  it  is  no  v/here 
eafily  feparated,  without  breaking  through  fome  of  the  mi^ 
nute  vehels  by  means  of  which  it  is  attached  to  the  bone. 


dura 


Part  V.  AND  NERVES.  381 

dura  mater  (m)  is  perfedlly  fmooth  and  melaftic, 
and  its  inner  furface  is  conftantly  bedewed  with 
a fine  pellucid  fluid,  which  eveiy  where  feparates 
it  from  the  pia  mater.  The  dura  mater  fends  oflT 
feveral  confiderable  procefles,  which  divide  the 
brain  into  feparate  portions,  and  prevent  them 
from  comprelfing  each  other.  Of  thefe  procefles 
thetjs  is  one  fuperior  and  longitudinal,  called  the 
falx^  or  falciform  procefs^  from  its  refemblance 
to  a fcythe.  It  arifes  from  the  fpine  of  the  os 
frontis,  near  the  chrifta  galli,  and  extending  along 
in  the  direction  of  the  fagittal  future,  to  beyond 
the  lambdoidal  future,  divides  the  brain  into  two 
hemifpheres.  A little  below  the  lambdoidal  fu- 
ture, it  divides  into  two  broad  wings  or  expan- 
fions  called  the  tranfuerfe  or  lateral  procejfes^ 
which  prevents  the  lobes  of  the  cerebrum  from 
prefling  on  the  cerebellum.  Befides  thefe  there 
is  a fourth,  which  is  fituated  under  the  tranf- 
verfe  proceifes,  and  being  continued  to  the  fpine 
of  the  occiput,  divides  the  cerebellum  into  two 
lobes. 

The 

(m)  This  membrane  is  commonly  defcribed  as  confifting 
of  two  laminae ; of  which  the  external  one  is  fuppofed  to 
perform  the  office  of  periofteum  internum  to  the  cranium, 
while  the  internal  one  forms  the  folds  and  procefles  of  the 
dura  mater.  In  the  natural  date,  however,  no  fuch  ffipara- 
tiefn  is  apparent  j like  other  membranes,  ;sve  may  indeed  di- 
vide it,  not  into  two  only,  but  many  lamintEj  but  this  divi- 
fion  is  artificial,  and  dejjends  on  the  dexterity  of  the  ana- 
tomift.. 


382  OF  THE  BRAIN  Pa rt  V. 

The  blood,  after  being  diftributed  through 
the  cavity  of  the  cranium  by  means  of  the  ar- 
teries, is  returned,  as  in  the  other  parts  of  the 
body,  by  veins  which  all  pafs  on  to  certain  chan- 
nels, (ituated  behind  thefe  feveral  procefles. 

Thefe  canals  or  iinufes  communicate  with  each 
other,  and  empty  themfeives  into  the  internal 
jugular  veins,  which  convey  the  blood  into^  the 
v£na  cava.  They  are  in  fa<^f  triangular  veins, 

' running  through  the  fubftance  of  the  dura  mater, 
and,  like  the  proceffes,  are  diRinguifhed  into 
longitudinal  and  lateral ; and  where  thefe  three 
meet,  and  where  the  fourth  procefs  paflTes  off,  we 
obferve  a fourth  fmus,  which  is  called  torcular  ; 
Herophilus,  who  firft  defcribed  it,  having  fup- 
pofed  that  the  blood  at  the  union  of  thel'e  two 
veins,  is,  as  it  were,  in  a prefs. 

Befides  tliefe  four  canals,  which  were  known 
to  the  ancients,  modern  anatomifts  enumerate 
many  others,  by  giving  the  appellation  of  finufes 
to  other  veins  of  the  dura  mater,  which  for  the 
moil  part  empty  themfeives  into  fome  of  thofe 
we  have  juft  now  defcribed.  There  are  the  in- 
ferior longitudinal  fmus,  the  fuperior  and  inferior 
]’>etrous  fmufes,  the  cavernous  fmufes,  the  circu- 
lar linus,  and  the  anterior  and  pofterior  occipital 
fmufes. 

Thefe  fmufes  or  veins,  by  being  conveyed 
through  a thick  denfe  membrane,  firmly  fufpend- 
ed,  as  the  dura  mater  is,  within  the  cranium, 
are  lefs  liable  to  rupture  ; at  the  fame  time  they 

3 


Part.  V.  AND  NERVES.  383 

■are  well  fupported,  and  by  running  every  where 
along  the  inner  furface  of  the  bones,  they  are 
prevented  from  prefling  on  the  fubftance  of  the 
•brain.  To  prevent  too  great  a dilatation  of  them, 
we  find  filaments  (called  chorda  Willifii^  from 
their  having  been  firft  noticed  by  Willis]  ftretch- 
ed  acrofs  their  cavities  ; and  the  oblique  manner 
in  which  the  veins  from  the  brain  run  through 
the  fubftance  of  the  brain  into  thefe  channels^ 
ferves  the  purpofe  of  a valve,  which  prevents 
the  blood  from  turning  back  into  the  fmaller  and 
weaker  veflels  of  the  brain. 

'T\\&pia  mater  is  a much  fofter  and  finer  mem- 
brane than  the  dura  mater ; being  exceedingly 
delicate,  tranfparent,  and  vafcular.  It  invefts 
every  part  of  the  brain,  and  fends  off  an  infinite 
number  of  elongations,  which  infinuate  th^m- 
felves  between  the  convolutions,  and  even  into 
the  fubftance  of  the  brain.  This  membrane  is 
compofed  of  two  larainse  ; of  which  the  exterior 
one  is  named  tunica  arachnoidea^  from  its  thin- 
neis,  which  is  equal  to  that  of  a fpider’s  web. 
Thefe  two  laminse  are  intimately  adherent  to  each 
Other  at  the  upper  part  of  the  brain,  but  are  eafily 
feparable  at  the  bafis  of  the  brain,  and  through 
the  whole  length  of  the  medulla  fpinalis.  The 
external  layer,  or  tunica  arachnoidea,  appears  to 
be  fpread  uniformly  over  the  furface  of  the  brain, 
but  without  entering  into  its  furrows  as  the  in- 
ner layer  does  ; the  latter  being  found  to  infinu- 
ate itfelf  between  the  convolutions,  and  even  into 

the 


384  OF  THE  BRAIN  Part  V. 

the  interior  cavities  of  the  brain.  The  blood- 
veffels  of  the  brain  are  diftributed  through  it  in 
their  way  to  that  organ,  and  are  therefore  divided 
into  very  minute  ramifications,  before  they  pene- 
trate the  fubftance  of  the  brain. 

There  are  feveral  parts  included  under  the  ge- 
neral denomination  of  brain.  One  of  thefe, 
which  is  of  the  fofteft  confiftence,  and  fills  the 
greateft  part  of  the  cavity  of  the  cranium,  is  the 
cerebrum.,  or  brain  properly  fo  called.  Another 
portion,  which  is  feated  in  the  inferior  and  pof- 
terior  part  of  the  head,  is  the  cerebellum  ; and  a 
third,  which  derives  its  origin  from  both  thefe, 
is  the  medulla  oblongata. 

The  cerebrum  is  a medullary  mafs  of  a mode- 
rate confiftence,  filling  up  exactly  all  the  upper 
part  of  the  cavity  of  the  cranium,  and  divided 
into  two  hemifpheres  by  the  falx  of  the  dura 
mater.  Each  of  thefe  hemifpheres  is  ufually  dif- 
tinguifhed  into  a7i  interior.,  a middle,  and  a pof- 
terior  lobe.  The  firft  of  thefe  is  lodged  on  the 
orbital  procefles  of  the  os  frontis ; the  middle 
lobes  lie  on  the  middle  foffse  of  the  bafis  of  the 
cranium,  and  the  pofterior  lobes  are  placed  on 
the  tranfverfe  feptum  of  the  os  occipitis,  imme- 
diately over  the  cerebellum,  from  which  they  are 
feparated  by  the  lateral  procefles  of  the  dura  ma- 
ter. Thefe  two  portions  afford  no  diftinguifhing 
mark  of  feparation  ; and  on  this  account  Haller, 
and  many  other  modern  anatomifts,  omit  the 

diftindtion 


PartV.  and  nerves.  385 

diftind;ion  of  middle  lobe,  and  fpeak  only  of  the 
anterior  and  pofterior  lobes  of  the  brain. 

The  cerebrum  appears  to  be  compofed  of  two 
diftindt  fubftances.  Of  thefe,  the  exterior  one, 
which  is  of  a greyifh  or  alh-colour,  is  called  the 
cortex^  and  is  fomev/hat  fofter  than  the  other, 
which  is  very  white,  and  is  called  medulla  or  fiib- 
Jlatitla  alba. 

After  having  removed  the  falx,  and  feparated 
the  two  hemifpheres  from  each  other,  we  per- 
ceive a white  convex  body,  the  corpus  callofum, 
which  is  a portion  of  the  medullary  fubftance, 
uniting  the  two ' hemifpheres  to  each  other,  and 
not  invefted  by  the  cortex.  By  making  an  ho- 
rizontal incifion  in  the  brain,  on  a level  with  this 
corpus  callofum,  we  'difeover  two  oblong  cavi- 
ties, named  the  anterior  or  lateral  ventricles.^  one 
in  each  hemifphere.  Thefe  two  ventricles, 
which  communicate  with  each  other  by  a hole 
immediately  under  the  plexus  choroides,  are  fe- 
parated laterally  by  a very  fine  medullary  parti- 
tion, called  feptum  lucidiim.^  from  its  thinnefs  and 
tranfparency.  The  lower  edge  of  this  feptum  is 
fixed  to  the  fornix,  v/hich  is  a kind  of  medullary 
arch  (as  its  name  implies)  fituated  under  the  cor- 
pus callofum,  and  nearly  of  a triangular  Ihape. 
Anteriorly  the  fornix  fends  off  two  medullary 
chords,  called  its  antc7-lor  crura  ; V\^hich  feem  to 
be  united  to  each  other  by  a portion  of  medulla- 
ry fubftance,  named  commijjlira  antej'ior  cerebri, 
Thefe  crura  diverging  from  one  another,  are  loft 

B b at 


386  OF  THE  BRAIN  Part  V. 

at  the  other  fide  of  the  lower  and  fore-part  of  the 
third  ventricle.  Pofteriorly  the  fornix  is  formed 
into  two  other  crura,  which  unite  with  two  me- 
dullary protuberances  called  pedes  bippocampiy 
and  Ibmetimes  CGrnaa  ammonls^  that  extend  along 
the  back-part  of  the  lateral  ventricles.  The 
concave  edge  of  the  pedes  hippocampi  is  co- 
vered by  a medullary  lamina,  called  corpus  fim- 
briahim. 

Neither  the  edges  of  the  fornix,  nor  its  pofte- 
rior  crura,  can  be  well  diftinguiflied,  till  we  have 
removed  the  plexus  choroides.  This  is  a pro- 
duction of  the  pia  mater,  which  is  fpread  over 
the  lateral  ventricles.  Its  loofe  edges  are  collect- 
ed, fo  as  to  appear  like  a vafcular  band  on  each 
fide. 

When  we  have  removed  this  plexus,  we 
difeover  feveral  other  protuberances  included  in 
the  lateral  ventricles.  Thefe  are  the  corpora 
ftriata,  the  thalami  nervorum  opticorum,  the 
tubercula  quadrugemina,  and  the  pineal  gland. 

The  corpora  Jlriata  are  two  curved  oblong  emi- 
nences, that  extend  along  the  anterior  part  of  the 
lateral  ventricles.  They  derive  their  name  from 
their  ftriated  appearance,  which  is  owing  to  an 
intermixture  of  the  cortical  and  medullary  fub- 
ftances  of  the  brain.  The  thalami  nervorum  op- 
iicorum,  are  fo  called,  becaufe  the  optic  nerves 
arife  chiefly  from  them,  and  they  are  likewife 
compol’ed  both  of  the  cortex  and  medulla.  They 
are  feparated  from  the  corpora  ftriata  only  by  a 

kind 


Part  V.  AND  NERVES.  387 

kind  of  medullary  chord,  the  geminum  centrum 
femi-circulare.  The  thalami  are  nearly  of  an 
oval  fhape,  and  are  fituated  at  the  bottom  of  the 
upper  cavity  of  the  lateral  ventricles.  They  are 
clofely  united,  and  at  their  convex  part  feem  to 
become  one  body. 

Anteriorly,  in  the  fpace  between  the  thalami, 
we  obferve  an  orifice  by  which  the  lateral  ven- 
tricles communicate,  and  another  leads  down 
from  this,  under  the  different  appellations  of 
foramen  commune  anterius^  vulva  iter  ad  infundi- 
btdiim^  but  more  properly  iter  ad  tertium  ventri- 
culiim  : and  the  feparation  of  the  thalami  from 
each  other  pofteriorly,  forms  another  opening  or 
interftice  called  anns.  This  has  been  fuppofed 
to  communicate  with  the  third  ventricle  ; but  it 
does  not,  the  bottom  of  it  being  fhut  up  by  the 
pia  mater.  The  back  part  of  the  anus  is  formed 
by  a kind  of  medullary  band,  which  connects  the 
thalami  to  each  other,  and  is  called  coimnijfura 
poferior  cerebri. 

Behind  the  thalami  and  commiffura  pofterior, 
we  obferve  a fmall,  foft,  greyifli,  and  oval  body, 
about  the  fize  of  a pea.  This  is  the  glandula  pi- 
nealis  ; it  is  defcribed  by  Galen  under  the  name 
of  conarion^  and  has  been  rendered  famous  by 
Defcartes,  who  fuppofed  it  to  be  the  feat  of  the 
foul.  Galen  feems  formerly  to  have  entertained 
the  fame  opinion.  Some  modern  writers  have, 
with  as  little  reafon,  imagined  that  the  foul  is 
placed  in  the  corpus  callofum. 

Bb  2 


The 


388  OF  THE  BRAIN  Part  V. 

The  pineal  gland  refts  upon  four  remarkable 
eminences,  difpofed  in  pairs,  and  feated  imme- 
diately below  it.  Thefe  tubercles,  which  by  the 
ancients  were  called  itfics  and  nates^  have,  fmce 
the  time  of  Winllovc,  beeii  more  commonly  nam- 
ed tnbercula  cm  a drug  emir/ a. 

Under  thethalami  we  obferve  another  cavity, 
the  third  ventricle,  which  terminates  anteriorly 
in  a fmall  medullary  canal,  the  infundibulum, 
that  leads  to  the  glandula  pituitaria.  it  has  been 
doubted,  whether  the  infundibulum  is  really  hol- 
low ; but  fome  late  experiments  on  this  part  of 
the  brain  by  ProfelTor  Murray  of  Upfal,  clearly 
prove  it  to  be  a medullary  canal,  furrounded  by 
both  laminse  of  the  pia  mater.  After  freezing 
the  brain,  this  channel  was  found  filled  with  ice  ; 
and  de  Haen  tells  "j'  us,  he  found  it  dilated,  and 
filled  with  a calcareous  matter  (n). 

The  foft  fpongy  body  in  which  the  infundibu- 
lum terminates,  was  by  the  ancients  fuppofed  to 
be  of  a.  glandular  firudiure,  and  deftined  to  filter 
the  ferofity  of  the  brain.  Spigelius  pretended 
to  have  diicovered  its  excretory  dudt,  but  it  feems 
certain  tliat  no  fuch  dudt  exifts.  It  is  of  an 

oblong 

* Difl).  de  Infundibula  Cerebri. 

I Ratio  Med.  tom.  vi.  p.  271. 

(n)  The  under  part  of  it,  however,  appears  to  be  imper- 
vious ; at  lead  no  injeftion  that  can  be  depended  on  has  been 
made  to  pafs  from  it  into  the  glandula  pituitaria  without  lace- 
ration of  parts. 


PartV.  and  nerves.  389 

oblong  fliape,  compofed,  as  it  were,  01  two 
lobes.  In  ruminant  animals  it  is  much  larger 
than  in  man. 

From  the  pofterior  part  of  the  third  ven- 
tricle, we  fee  a fmall  gTOOve  or  channel,  de- 
feending  obliquely  backwards.  This  channel, 
which  is  called  the  aqueduct  oj  Sylvias^  though  it 
was  known  to  the  ancients,  opens  into  another 
cavity  of  the  brain,  placed  between  the  cerebel- 
lum and  medulla  oblongata,  and  called  the  foiii'ih 
ventricle. 

The  cerehelliim.,  v/hich  is  divided  into  two 
lobes,  is  commonly  fuppofed  to  be  of  a firmer 
texture  than  the  cerebrum  ; but  the  truth  is, 
that  in  the  greater  number  of  fubjedts,  there  ap- 
pears to  be  no  fenfible  difference  in  the  con- 
liftence  of  fhefe  two  parts.  It  has  more  of  the 
cortical  than  of  the  medulku-y  iubftance  in  its 
compofition. 

The  furrow  that  divides  the  two  lobes  of  the 
cerebellum  leads  anteriorly  to  a prccefs,  compof- 
ed  of  medullary  and  cortical  fubllances,  covered 
by  the  pia  mater  ; and  which,  from  its  being  di- 
vided into  numerous  furrow's,  refembling  the 
rings  of  the  earth-worm,  is  named  p'occfj'us  ver- 
mifermis.  This  procefs  forms  a kind  of  ring  in 
its  coude  between  the  lobes. 

•*.  The  furface  of  the  cerebellum  does  not  af- 
ford thofe  circumvolutions  which  appear  in  the 
cerebrum  ; but  infeead  of  thefe,  vre  cbferve  a 
great  number  of  minute  furrow's,  running  pa- 


390  OF  THE  BRAIN  Part  V. 

rallel  to  each  other,  and  nearly  in  a tranfverfe  di- 
redion.  The  pia  mater  infmuates  itfelf  into 
thefe  furrows. 

When  we  cut  into  the  fubftance  of  the  cere- 
bellum, from  above  downwards,  we  find  the 
medullary  part  running  in  a kind  of  ramifying 
courfe,  and  exhibiting  an  appearance  that  has 
gotten  the  name  of  arbor  vita.  Thefe  ramifi- 
cations unite  to  form  a medullary  trunk ; the 
the  middle,  anterior,  and  mofi;  confiderable  part 
of  which  forms  tv/o  procelTes,  the  crura  cerebel- 
li,  which  unite  with  the  crura  cerebri,  to  form 
the  medulla  oblongata.  The  laft  furnifhes  two 
other  proceiTes,  which  lofe  themfelves  under  the 
nates,  and  thus  unite  the  lobes  of  the  cerebellum 
to  the  pofterior  part  of  the  cerebrum.  Under 
the  nates  we  obferve  a tranfverfe  medullary  line, 
or  linea  alba,  running  from  one  of  thefe  procefles 
to  the  other  ; and  between  them  we  find  a very 
thin  medullary  lamina,  covered  with  the  pia  ma- 
ter, which  the  generality  of  anatomifls  have 
(though  feemingly  without  reafon)  confidered 
as  a valve  formed  for  clofing  the  communica- 
tion between  the  fourth  ventricle  and  the  aquae- 
dudus  Sylvii.  Vieufiens  named  it  valvula  ma- 
jor cerebri. 

The  medulla  oblongata  is  fituated  in  the  mid- 
dle, lower,  and  pofterior  part  of  the  cranium, 
and  may  be  confidered  as  a produftion  or  con- 
tinuation of  the  whole  medullary  fubftance  of 
the  cerebrum  and  cerebellum,  being  formed  by 

the 


Part  V.  AND  NERVES.  391 

the  of  two  confiderable  medullary  procefies  of 
the  cerebrum,  called  crii7~a  cerebri.,  with  two 
other  fmaller  ones  from  the  cerebellum,  which 
were  juft  now  fpoken  of  under  the  name  of 
crura  cerebellL 

The  crura  cerebri  arife  from  the  middle  and 
lower  part  of  each  hemifphere.  They  are  fepa- 
rated  from  each  other  at  their  origin,  but  are 
united  below,  where  they  terminate  in  a middle 
protuberance,  xhtponsVaroUi.,  fo  called,  becauie 
Varolius  compared  it  to  a bridge.  This  name, 
however,  can  convey  no  idea  of  its  real  appear- 
ance. It  is,  in  faft,  nothing  more  than  a me- 
dullary protuberance,  nearly  of  a femi-fpherical 
fhape,  which  unites  the  crura  cerebri  to  thofe  of 
the  cerebellum. 

Between  the  crura  cerebri,  and  near  the  ante- 
rior edge  of  the  pons  Yarolii,  are  two  tubercles, 
compofed  externally  of  medullary,  and  internal- 
ly of  cineritious  fubftance,  to  which  Euftachius 
firft  gave  the  name  of  emme?itia  mamillares. 

Along  the  middle  of  the  pofterior  furface  of 
the  medulla  oblongata,  where  it  forms  the  ante- 
rior part  of  the  fourth  ventricle,  we  obfer ve  a 
kind  of  furrow  which  runs  downwards  and  ter- 
minates in  a point.  About  an  inch  above  the 
lower  extremity  of  this  ftlfure,  feveral  medullary 
filaments  are  to  be  feen  running  towards  it  on 
each  fide  in  an  oblique  dirediion,  fo  as  to  give 
it  the  appearance  of  a writing-pen ; hence  it  is 
called  calamus  fcriptorius. 


From 


392  OF  THE  BRAIN.  Part  V. 

From  the  pofterior  part  of  the  pons  Varolii, 
the  medulla  oblongata  defeends  obliquely  back- 
wards ; at  its  fore -part,  immediately  behind  the 
pons  Varolii,  we  obferve  two  pair  of  eminences, 
Vv'hich  were  defcribed  by  Euftachius,  but  receiv- 
ed no  particular  appellation  till  the  time  of  Vi- 
euffens,  who  gaAm  them  the  names  of  corpora 
ouvaria  and  corpora  pyramidalia.  The  former 
are  the  outermoft,  being  placed  one  on  each  fide. 
They  are  nearly  of  an  oval  ihape,  and  are  com- 
pofed  of  medulla,  with  ttreaks  of  cortical  fub- 
ftance.  Between  thefe  are  the  corpora  pyra- 
midalia, each  of  which  terminates  in  a point. 
In  the  human  fubjed;  thefe  four  eminences  are 
fometimes  not  eafiiy  diftinguifned. 

The  medulla  fpinalis^  or  Jpinal  marrow^  which 
is  the  name  given  to  the  medullary  chord  that 
is  extended  down  the  vertebral  canal,  from  the 
great  foramen  of  the  occipital  bone  to  the  bot- 
tom of  the  lafl;  lumbar  vertebra,  is  a continua- 
tion of  the  medulla  oblongata.  Like  the  other 
parts  of  the  brain,  it  is  invefted  by  the  dura  and 
pia  mater.  The  firft  of  thefe,  in  its  paffage  out 
of  the  cranium,  adheres  to  the  foramen  of  the 
03  occipids.  Its  connedion  with  the  ligamentary 
fubftance  that  lines  the  cavity  of  the  fpine,  is  on- 
ly by  means  of  cellular  membrane  ; but  between 
the  ieveral  vertebras,  where  the  nerves  pafs  out 
of  die  fpine,  it  fends  off  prolongations,  which 
adhere  ftrongly  to  the  vertebral  ligaments.  Here, 
as  in  the  cranium,  the  dura  mater  has  its  finufes 

or 


PartV.  and  nerves.  393 

or  large  veins.  Thefe  are  two  in  number,  and 
are  feen  running  on  each  fide  of  the  medullary 
column,  from  the  foramen  magnum  of  the  os 
occipitis  to  the  lower  part  of  the  os  facriim.  They 
communicate  together  by  ramifying  branches  at 
each  vertebra,  and  terminate  in  the  vertebral, 
intercoftal,  and  facral  veins. 

The  pia  mater  is  connefiied  with  the  dura  ma- 
ter by  means  of  a thin  tranfparent  fubftance, 
which  from  its  indentations  between  the  fpinal 
nerves  has  obtained  the  name  of  ligamentum  den- 
tic  iilat  uni.  It  is  fo  me  what  firmer  than  the  tu- 
nica arachnoidea,  but  in  other  refpefls  refem- 
bles  that  membrane.  Its  ufe  is  to  fupport  the  fpi- 
nal  marrow,  that  it  may  not  affed:  the  medulla 
oblongata  by  its  weight. 

The  fpinal  marrow  itfelf  is  externally  of  a 
white  colour  ; but  upon  cutting  into  it  we  find 
its  middle-part  compofed  of  a darker  coloured 
mafs,  refembling  the  cortex  of  the  brain.  When 
the  marrow  has  reached  the  hrft  lumbar  verte- 
bra, it  becomes  extremely  narrow,  and  at  length 
terminates  in  an  oblong  protuberance  ; from  the 
extremity  of  which  the  pia  mater  fends  off  a 
prolongation  or  ligament,  refembling  a nerve, 
that  perforates  the  dura  mater,  and  is  fixed  to 
the  os  coccygis. 

The  medulla  fpinalis  gives  rife  to  30  or  3 1 
pair  of  neiwes,  but  they  are  not  all  of  the  fame 
fize,  nor  do  they  all  fun  into  in  the  fame  direc- 
tion. The  upper  ones  are  thinner  than  the  refl, 

and 


394  THE  BRAIN  Part  V. 

and  are  placed  almoft  tranfverfely : as  we  defcend 
we  find  them  running  more  and  more  obliquely 
downwards,  till  at  length  their  courfe  is  almoft 
perpendicular,  fo  that  the  lowermoft  nerves  ex- 
hibit an  appearance  that  is  called  cauda  equina^ 
from  its  refemblance  to  a horfe’s  tail. 

The  arteries  that  ramify  through  the  different 
parts  of  the  brain,  are  derived  from  the  inter- 
nal carotid  and  from  the  vertebral  arteries.  The 
medulla  fpinalis  is  fupplied  by  the  anterior  and 
pofterior  fpinal  arteries,  and  likewife  receives 
branches,  from  the  cervical,  the  inferior  and  fu- 
perior  intercoftal,  the  lumbar,  and  the  facral  ar- 
.teries. 

Sect.  II.  Of  the  Nerves. 

The  nerves  are  medullary  chords,  differing 
from  each  other  in  fize,  colour,  and  confiftence, 
•and  deriving  their  origin  from  the  medulla  ob- 
longata and  medulla  fpinalis.  There  are  39,  and 
fometimes  40,  pair  of  thefe  nerves  ; nine  (o)  of 
which  originate  from  the  medulla  oblongata,  and 
30  or  3 1 from  the  medulla  fpinalis.  They  ap- 
pear to  be  perfedxly  inelaftic,  and  likewife  to  pof- 

fefs 

(o)  It  has  been  ufual  to  defcribe  the  ten  pair  of  nerves  as 
arihng  from  the  medulla  oblongata;  but  as  the  tenth  pair 
arile  in  the  fame  manner  as  the  otl^er  fpinal  nerves,  Santorini, 
Heifter,  Halier,  and  others,  feem  very  properly  to  have 
clalTed  them  among  the  nerves  of  the  fpine. 


PartV.  and  nerves.  395 

fefs  no  irritability.  If  we  irritate  mufcular 
bres,  they  immediately  contradl ; but  nothing 
of  this  fort  happens  if  we  irritate  a nerve.  They 
carry  with  them  a covering  from  the  pia  mater; 
but  derive  no  tunic  from  the  dura  mater,  as  hath 
been  generally,  though  erroneoufly,  fuppofed, 
ever  fmce  the  time  of  Galen  (p),  the  outer  cover- 
ing of  the  nerves  being  in  fa£t  /nothing  more 
than  the  cellular  membrane.  This  covering  is 
very  thick  where  the  nerve  is  expofed  to  the 
adtion  of  mufcles  ; but  where  it  runs  through  a 
bony  canal,  or  is  fecure  from  prelTure,  the  cel- 
lular tunic  is  extremely  thin,  or  altogether  want- 
ing. We  have  inftances  of  this  in  the  portio 
mollis  of  the  auditory  nerve,  and  in  the  nerves 
of  the  heart. 

By  elevating,  carefully  and  gently,  the  brain 
from  the  bafis  of  the  cranium,  we  find  the  firft 
nine  pair  arifmg  in  the  following  order  : i . The 
nervi  olfadforii,  diftributed  through  the  pituita- 
ry membrane,  vv^hich  conftitutes  the  organ  of 
fmell.  2.  The  optici,  which  go  to  the  eyes,  where 
they  receive  the  impreffions  of  vifible  objedis. 
3.  The  oculorum  motores,  fo  called  becaufe  they 
are  diftributed  to  the  mufcles  of  the  eye.  4. 

The 

(p)  Baron  Haller  and  ProfefTor  Zinn  feem  to  have  been 
the  firll;  who  demonftrated,  that  the  dura  mater  is  reflefted 
upon  and  adheres  to  the  periofteum  at  the  edges  of  the  fora- 
mina that  afford  a palTage  to  the  nerves  out  of  the  cranium, 
and  vertebral  canal,  or  is  foon  loft  in  the  cellular  fubftance. 


396  OF  THE  BRAIN  Part  V. 

The  patheticl,  diftributed  to  the  fuperior  oblique 
mufcles  of  the  eyes,  the  motion  of  which  is 
expreffive  of  certain  paffions  of  the  foul.  5.  The 
nerves  of  this  pair  foon  divide  into  three  prin- 
cipal branches,  and  each  of  thefe  has  a different 
name.  Its  upper  divifion  its  he  ophthalamicus, 
which  is  diffributed  to  various  parts  of  the  i 
eyes,  eye-lids,  forehead,  nofe,  and  integu-  | 
ments  of  the  face.  The  fecond  is  called  the  > 
maxillaris  fiiperior^  and  the  third  maxUlaris  in- 
ferior ; both  of  which  names  allude  to  their  dif- 
tribution.  6.  The  abdudtores ; each  of  thefe 
nerves  is  diftributed  to  the  abductor  mufcle  of 
the  eye,  fo  called,  becaufe  it  helps  to  draw  the 
globe  of  the  eye,  from  the  nofe.  y.  The 
auditorii  (q^),  which  are  diftributed  through 
the  organs  of  hearing.  8.  The  par  vagum, 
which  derives  its  name  from  the  great  number  of 
parts  to  vrhich  it  gives  branches  both  in  the  tho- 
rax and  abdomen.  9.  The  linguales,  or  hypo- 
gloffi,  which  are  diftributed  to  the  tongue,  and 

appear 

(o^)This  pair, foon  after  its  entrance  into  the  meatus  audi- 
Eorius  internus,  feparates  into  two  branches.  One  of  thefe 
is  of  a very  foft  and  pulpy  confiftence,  it  is  called  the 
KZ3//.V  of  the  feventh  pair,  and  is  fpread  over  the  inner  part 
of  the  ear.  The  other  paiTes  out  through  the  aquednft  of 
Tallopius  in  a firm  chord,  which  is  difiinguiflied  as  the  por- 
tio  dura,  and  is  diftributed  to  the  external  ear  and  other 
pafts  of  the  neck  and  face. 


Part  V.  AND  NERVES.  397 

appear  to  contribute  both  to  the  organ  of  tafte 
and  to  the  motions  of  the  tongue  (r). 

It  has  already  been  obferved,  that  the  fpinai 
marrow  fends  off  30  or  31  pair  of  nerves ; thefe 
are  chiefly  diftributed  to  the  exterior  parts  of  the 
trunk  and  to  the  extremities.  They  are  com- 
monly diftinguiflied  into  the  cervical^  dorfal, 
lumbar^  and.  facral  nerves.  The  ceiwical,  which 
pafs  out  from  between  the  feveral  vertebrs  of 
the  neck,  are  eight  (s)  in  number ; the  dorfal, 
twelve  ; the  lumbar  five  ; and  the  facral,  five  or 
fix  ; the  number  of  the  latter  depending  on  the 
number  of  holes  in  the  os  facrum.  Each  fpinai 
nerve  at  its  origin  is  compofed  of  two  fafciculi  of 
medullary  fibres.  One  of  thefe  fafciculi  arifes 
from  the  anterior,  and  the  other  from  the  pof- 
terior  furface  of  the  medulla.  Thefe  fafciculi 

are 

(r)  Heifter  has  fummed  up  the  uTes  of  thefe  nine  pair  of 
nerves  in  the  two  following  Latin  verfes  : 

Glfaciens,  cernens,  oculofque  noveiis,  patienfquc, 

“ Caftans,  abducens,  audienjque,  vaganfque ^ loquevfque.'" 

(s)  Bcfidcs  thcle,  there  is  another  pair  called  acceft'-v  'n,  which 
arifes  from  the  medulla  fpinalis  at  its  beginning  ; and  alcending 
the  great  foramen  of  the  os  occipitis  into  the  cranium,  pafles 
out  again  clofe  to  the  eighth  pair,  with  which,  however,  it 
does  not  unite  ; and  it  is  afterwards  diilributcd  chiefly  to  the 
mufclesof  the  neck,  back,  and  fcapiila.  In  this  courfe  it  fends 
off  filaments  to  different  parts,  and  likewife  communicates  with 
feveral  other  nerves.  Phyfiologiffs  are  at  a lofs  liow  to  account 
for  the  fingular  origin  and  courfe  of  thefe  nervi  accefibrii.  The 
ajicients  confidered  them  as  a branches  of  the  eighth  pair,  dif- 
tributed to  mufcles  of  the  fcapnla  ; Willis  likewife  confidered 
them  as  appendages  to  that  pair,  and  on  that  account  named 
them  accefforii.  They  are  fomeiimes  called  the  fpinai  pair  ; 
but  as  this  latter  name  is  applicable  to  all  the  nerves  of  the  fpinc 
iudifcriminately,  it  feems  better  to  adopt  that  given  by  Wiilis. 


398  OF  THE  BRAIN  PartV. 

are  feparated  by  the  ligamentum  denticulatum ; 
after  which  we  find  them  contiguous  to  one  ano- 
ther. They  then  perforate  the  dura  mater,  and 
unite  to  form  a confiderable  knot  or  ganglion. 
Each  oi  thefe  ganglions  fends  off  two  branches  ; 
one  anterior,  and  the  other  pofterior.  The  an- 
terior branches  communicate  with  each  other  at 
their  coming  out  of  the  fpine,  and  likewife  fend 
off  one,  and  fometimes  more  branches,  to  affift 
in  the  formation  of  the  intercoftal  nerve. 

The  knots  or  ganglions  of  the  nerves  juft 
now  fpoken  of,  are  not  only  to  be  met  with  at 
their  exit  from  the  fpine,  but  likewife  in  various 
parts  of  the  body.  They  occur  in  nerves  of 
the  medulla  oblongata,  as  well  as  in  thofe 
of  the  fpine.  They  are  not  the  effedfs  of  dif- 
eafe,  but  are  to  be  met  with  in  the  fame  parts 
of  the  fame  nerves,  both  in  the  foetus  and  adult. 
They  are  commonly  of  an  oblong  ftiape,  and 
of  a greyifli  colour,  fomewhat  inclined  to  red, 
which  is  perhaps  owing  to  their  being  extreme- 
ly vafcular.  Internally  we  are  able  to  diftinguifh 
fomething  like  an  intermixture  of  the  nervous 
filaments. 

Some  writers  have  confidered  them  as  fo  ma- 
ny little  brains ; Lancifi  fancied  he  had  difeo- 
vered  mufcular  fibres  in  them,  but  they  are  cer- 
tainly not  of  an  irritable  nature.  A late  writer, 
Dr.  Johnftone*,  imagines  they  are  intended  to 
deprive  us  of  the  power  of  the  will  over  cer- 
tain 

* ElTay  on  the  Ufe  of  the  Ganglions  of  the  Nerves. 


Part  V.  AND  NERVES.  399 

tain  parts,  as  the  heart,  for  inftance  : but  if  this 
hypothefis  were  well  founded,  we  fhould  meet 
with  them  only  in  the  nerves  leading  to  involun- 
tary mufcles ; whereas  it  is  certain,  that  the  vo- 
luntary mufcles  receive  their  nerves  through  gan- 
glions. Dodtor  Monro,  from  obferving  the  ac- 
curate intermixture  of  the  minute  nerves  which 
coihpofe  them,  confiders  them  as  new  fources  of 
nervous  energy 

The  nerves,  like  the  blood-veffels,  in  their 
courfe  through  the  body,  communicate  with 
each  other ; and  each  of  thefe  communications 
conftitutes  wTat  is  called  a plexus^  from  whence 
branches  are  again  detached  to  different  parts  of 
the  body.  Some  of  thefe  are  conftant  and  con- 
fiderable  enongh  to  be  diftinguifhed  by  particu- 
lar names,  as  the  femilunar  plexus ; the  pulmo- 
nary plexus  ■,  hepatic^  cardiac,  &c. 

It  would  be  foreign  to  the  purpofe  of  this 
work,  to  follow  the  nerves  through  all  their  dif- 
tributions ; but  it  may  be  remembered,  that  in 
defcribing  the  different  vifcera,  mention  was 
made  of  the  nerves  diftributed  to  them.  There 
is  one  pair,  however,  called  the  intcrcojlal  or 
great  Sympathetic  nerve,  which  feems  to  require 
particular  notice,  becaufe  it  has  an  almoft  uni- 
verfal  conned;ion  and  correfpondence  with  all 
the  other  nerves  of  the  body.  Authors  are  not 
perfectly  agreed  about  the  origin  of  the  intercof- 

tal  ; 


f Obfervations  oa  the  Nervous  fyftem. 


400  OF  THE  BRAIN  Part  V. 

tal ; but  it  may  perhaps  not  improperly  be  de- 
fcribed,  as  beginning  from  filaments  of  the  fifth 
and  fixth  pair  ; it  then  pafl'es  out  of  the  cranium, 
through  the  bony  canal  of  the  carotid,  from 
whence  it  defcends  laterally  clofe  to  the  bodies 
of  the  vertebrsE,  and  receives  branches  from  al- 
moft  all  the  v ertebral  nerves  ; forming  almoft  as 
many  ganglions  in  its  courfe  through  the  thorax 
and  abdomen.  It  fends  oft  an  infinite  number 
of  branches  to  the  vifcera  in  thofe  cavities,  and 
forms  feveral  plexufes  with  the  branches  of  the 
eight  pair  or  par  vagum. 

That  the  nerves  are  deftined  to  convey  the 
principles  of  motion  and  fenfibility  to  the  brain 
from  all  parts  of  the  fyftem,  there  can  be  no 
doubt ; but  how'  thefe  effedts  are  produced,  no 
one  has  ever  yet  been  able  to  to  determine.  The 
inquiry  has  been  a conftant  fource  of  hypothe- 
fis  in  all  ages,  and  has  produced  fome  ingenious 
ideas,  and  many  erroneous  pofitions,  but  with- 
out having  hitherto  afforded  much  fatisfadlory 
information. 

Some  phyfiologifts  have  ponfidered  a trunk  of 
nerves  as  a folid  chord,  capable  of  being  divided 
into  an  infinite  number  of  filaments,  by  means 
of  which  the  impreffions  of  feeling  are  convey- 
ed to  the  fenforium  commune.  Others  ha,ve 
fuppofed  it  to  be  a canal,  which  afterwards  fe- 
paratesinto  more  minute  channels  ; or,  perhaps, 
as  being  an  aiTemblage  of  many  very  fmall  and 
diftindl  tubes,  conneded  to  each  other,  and  thus 
3 forming 


Part  V,  AND  NERVES.  401 

forming  a cylindrical  chord.  They  who  con- 
tend for  their  being  folid  bodies,  are  of  opinion 
that  feeling  is  occafioned  by  vibration  ; fo  that, 
for  inftance,  according  to  this  fyftem,  by  prick- 
ing the  finger,  a vibration  would  be  occafioned 
in  the  nerve,  diftributed  through  its  fubftance ; 
and  the  effects  of  this  vibration,  when  extended 
to  the  fenforium,  would  be  an  excital  of  pain. 
But  the  inelafticity,  the  foftnefs,  the  connexion, 
and  the  fituation  of  the  nerves,  are  fo  many 
proofs  that  vibration  has  no  fhare  in  the  caufe  of 
feeling. 

Others  have  fuppofed,  that  in  the  brain  and 
fpinal  marrow,  a very  fubtile  fluid  is  fecreted, 
and  from  thence  conveyed  through  the  imper- 
ceptible tubes,  which  they  confider  as  exilling 
in  the  nerves.  They  have  farther  fuppofed, 
that  this  very  fubtile  fluid,  to  which  they  have 
given  the  name  of  animal fpirits^  is  fecreted  in 
the  cortical  fubftance  of  the  brain  and  fpinal 
marrow,  from  whence  it  paffes  through  the  me- 
dullary fubftance.  This,  like  the  other  fyftem, 
is  founded  altogether  on  hypothefis ; but  it 
feems  to  be  an  hypothefis  derived  from  much 
more  probable  principles,  and  there  are  many 
ingenious  arguments  to  be  brought  in  its  fup- 
port. 


C c 


EXPLA- 


402 


OF  THE  BRAIN 


Part  V. 


EXPLANATION  or  PLATE  XXIX. 

Eig.  1.  Reprefents  the  inferior  part  of  the 
brain  ;-~thc  Anterior  part  of  the  whole  Spine, 
including  the  Medulla  Spinalis  ; — with  the  ori- 
gin and  large  portions  of  all  the  Nerves. 

A A,  Ihe  anterior  lobes  of  the  cerebrum. 
B B,  The  lateral  lobes  of  the  cerebrum.  C C, 
The  two  lobes  of  the  cerebellum.  D,  Tuber 
annulare.  E,  The  pafl'age  from  the  third  ven- 
tricle to  the  infundibulum.  F,  The  medulla  ob- 
longata, which  fends  off  the  medulla  fpinalis 
through  the  fpine.  G G,  That  part  of  the  os 
occipitis  which  is  placed  above  (H  H)  the  tranf- 
verfeproceflesofthefirfl;  cervical  vertebra.  II,&c. 
The  feven  cervical  vertebrse,  with  their  interme- 
diate cartilages.  K K,  &c.  The  twelve  dorfal 
vertebrse,  with  their  intermediate  cartilages.  L L, 
&c.  The  five  lumbar  vertebrse,  with  their  in- 
termediate cartilages.  M,  The  osfacrum.  N, 
The  oscoccygis. 

Nerves. — i i.  The  firft  pair  of  nerves, 
named  olfacl'ory^  which  go  to  the  nofe.  2 2,  The 
fecond  pair,  named  optic^  which  goes  to  form 
ihe  tunica  retina  of  the  eye.  3 3,  The  third, 
named  motor  oculi ; it  fupplies  moil  of  the  muf- 
des  of  the  eye-ball.  4 4,  The  fourth  pair, 
named  pathdic^ — which  is  wholly  fpent  upon 
the  muictilus  trochlearis  of  the  eye.  5 5,  The 

fifth 


Part  V.  AND  NERVES.  403 

fifth  pair  divides  into  three  branches. — The  firft, 
named  ophthalmic^  goes  to  the  orbit,  fupplies  the 
lachrymal  gland,  and  fends  branches  out  to  the 
forehead  and  nofe. — The  fecond,  named  fupe- 
rior  maxillary^  fupplies  the  teeth  of  the  upper 
jaw,  and  fome  of  the  mufcles  of  the  lips. — The 
third  named  mferior  maxillary^  is  fpent  upon  the 
mufcles  and  teeth  of  the  lower  jaw,  tongue,  and 
mufcles  of  the  lips.  6 6,  The  fixth  pair,  which, 
after  fending  olf  the  beginning  of  the  intercof- 
tal  or  great  fympathetic,  is  fpent  upon  the  ab- 
ductor oculi.  7 7,  The  feventh  pair,  named  au- 
ditory^ divides  into  two  branches. — The  largeft, 
named7'or//o  mollis^  is  fpent  upon  the  internal 
ear. — The  fmalleft,  portio  diira^  joins  to  the 
fifth  pair  within  the  internal  ear  by  a reflected 
branch  from  the  fecond  of  the  fifth  ; and  with- 
in the  tympanum,  by  a branch  from  the  third 
of  the  fifth,  named  chorda  tympa7ii. — ^Vid.  fig. 
3.  near  B.  8 8,  &c.  The  eighth  pair,  named 
par  vagum, — which  accompanies  the  intercoftal, 
and  is  fpent  upon  the  tongue,  larynx,  pharynx, 
lungs,  and  abdominal  vifcera.  9 9,  The  ninth 
pair,  which  are  fpent  upon  the  tongue.  1010, 
&c.  The  intercofial,  or  great  fympathetic, 
which  is  feen  from  the  fixth  pair  to  the  bottom 
of  the  pelvis  on  each  fide  of  the  fpine,  and 
joining  with  all  the  nerves  of  the  fpine  ; — in  its 
progrefs  fupplying  the  heart,  and,  with  the  par 
vagum,  the  contents  of  the  abdomen  and  pelvis. 
II,  II,  The  accefforius,  which  is  fpent  upon 
C c 2 the 


404  OF  THE  BRAIN  Part  V. 

tlie  ftemocleidomafloidEEiis  and  trapezius  muf- 
cles.  12  12,  The  hrft  cervical  nerves  ; — 13  1 3, 
The  fecond  cervical  nerves ; — both  fpent  up- 
on the  mufcles  that  lie  on  the  neck,  and  te- 
guments of  the  neck  and  head.  14  14,  The  third 
cervical  nerves,  which,  after  fending  off  (15  15, 
&c.)  the  phrenic  nerves  to  the  diaphragm,  fupply 
the  mufcles  and  teguments  that  lie  on  the  fide 
of  the  neck  and  top  of  the  Ihoulder.  16  16, 
The  brachial  plexus,  formed  by  the  fourth,  fifth, 
fixth,  feventh  cervicals,  and  firft  dorfal  nerves. 

■ — which  fupply  the  mufcles  and  teguments  of 
the  fuperior  extremity,  ij  The  twelve 
dorfal,  or  proper  intercoftal  nerves,  which  are 
fpent  upon  the  intercoftal  mufcles  and  fome  of 
the  large  mufcles  which  lie  upon  the  thorax. 
1818,  The  five  lumbar  pairs  of  nerves,  w'hich 
fupply  the  lumbar  and  abdominal  mufcles,  and 
fome  of  the  teguments  and  mufcles  of  the  infe- 
rior extremity.  19  19?  The  facro-fciatic,  or 
poilerior  crural  nerve,  formed  by  the  two  infe- 
rior lumbar,  and  three  fuperior  of  the  os  facrum. 
This  large  nerve  fupplies  the  greateft  part  of  the 
mufcles  and  teguments  of  the  inferior  extremity. 
20,  The  ftomachic  plexus,  formed  by  the  eighth 
pair.  2121,  Branches  of  the  folar  or  cseliac 
plexus,  formed  by  the  eighth  pair  and  intercof- 
tals,  which  fupply  the  ftomach  and  chylopoietic 
vifccra.  22  22,  Branches  of  the  fuperior  and 
inferior  mefenteric  plexufes,  formed  by  the  eighth 
pair  and  intercoftals,  which  fupply  the  chylo- 
poietic vifcera,  with  part  of  the  organs  of  urine 

and 


Plate  XXIX 


Part  V.  AND  NERVES.  405 

and  generation.  23  23,  Nerves  which  accom- 
pany the  fphermatic  chord.  24  24,  The  hypo- 
gaftric  plexus,  which  fupplies  the  organs  of  u- 
line  and  generation  within  the  pelvis. 

Fig.  2,  3,  4,  5.  Shows  different  Views  of  the 
Inferior  part  of  the  Brain,  cut  perpendicular- 
ly through  the  Middle, — ^with  the  origin  and 
large  Portions  of  the  Nerves  which  pafs  out 
through  the  bones  of  the  Cranium, — and  the 
three  firft  Cervical. 

A,  The  anterior  lobe.  B,  The  lateral  lobe  of 
the  cerebrum.  C,  One  of  the  lobes  of  the  ce- 
rebellum. D,  Tuber  annulare.  E,  Corpus  py- 
ramidale,  in  the  middle  of  the  medulla  oblon- 
gata. F,  The  corpus  olivare,  in  the  fide  of  the 
medulla  oblongata.  G,  The  medulla  oblongata. 
H,  The  medulla  fpinalis. 

Nerves. — i 2345678  and  9,  Pairs  of  nerves. 
10  10,  Nervus  accefforius,  which  comes  from 
— II,  12,  and  13,  The  three  firft  cervical 
gaerves. 


Part  VI. 


4o6 


OF  THE  SENSES  Part  VI. 


PART  VI. 

Of  the  senses,  and  their  ORGANS. 

IN  treating  of  the  fenfes,  we  mean  to  confine 
ourfelves  to  the  external  ones  of  touchy  tajie, 
fmdlhig^  hearings  and  vifion.  The  word  fenje, 
when  applied  to  thefe  five,  feems  to  imply  not 
only  the  fenfation  excited  in  the  mind  by  certain 
impreffions  made  on  the  body,  but  likewife  the 
organ  deftined  to  receive  and  tranfmit  thefe  im- 
preflions  to  the  fenforium.  Each  of  thefe  or- 
gans being  of  a peculiar  fl;ru<Ture,  is  fufcepti- 
ble  only  of  particular  impreffions,  which  will  be 
pointed  out  as  we  proceed  to  defcribe  each  of 
them  feparately. 

Sect.  I.  Of  Touch. 

The  fenfe  of  touch  may  be  defined  to  be  the 
faculty  of  diftinguiffiing  certain  properties  of  bo- 
dies by  the  feel.  In  a general  acceptation,  this 
definition  might  perhaps  not  improperly  be  ex- 
tended to  every  part  of  the  body  poffeffed  of 
fenfibility  (t),  but  it  is  commonly  confined  to 

the 

(t)  In  the  courfe  of  this  article,  mention  has  often  been 
made  of  the  fenfibility  or  infenfibility  of  different  parts  of 
the  body  : it  will  therefore,  perhaps,  not  be  amifs  to  obferve 


Part  VI.  AND  THEIR  ORGANS.  407 
the  nervous  papillee  of  the  cutis,  or  true  Ikin, 
which,  with  its  appendages,  and  their  feveral 
ufes,  have  been  already  defcribed. 

The  exterior  properties  of  bodies,  fuch  as 
their  folidity,  moifture,  inequality,  fmoothnefs, 
drynefs,  or  fluidity,  and  likewife  their  degree  of 
heat,  feem  all  to  be  capable  of  making  different 
impreflions  on  the  papilla,  and  confequently  of 
exciting  different  ideas  in  the  fenforium  com- 
mune. But  the  organ  of  touch,  like  all  the 
other  fenfes,  is  not  equally  delicate  in  every 
part  of  the  body,  or  in  every  fubjefl ; being  in 
fome  much  more  exquifite  than  it  is  in  others. 

Sect. 


in  this  place,  that  many  parts  which  were  formerly  fuppof- 
ed  to  poflefs  the  moft  exquifite  fenfe.  are  now  known  to 
have  but  little  or  no  feeling,  at  leaf;  in  a found  ftate:  for  in 
an  inflamed  ftate,  even  the  bones,  the  moft  infenflble  parts 
of  any,  become  fufceptible  of  the  moft  painful  fenfations. 
This  curious  difeovery  is  due  to  the  late  Baron  Haller.  His 
experiments  prove,  that  the  bones,  cartilages,  ligaments, 
tendons,  epidermis,  and  membranes  (as  the  pleura,  pericar- 
dium, dura  and  pia  mater,  periofteum,  8cc.)  may  in  a healthy 
ftate  be  confidered  as  infenflble.  As  fenfibility  depends  on 
the  brain  and  nerves,  of  courfe  dilFcrent  parts  will  polTefs 
a greater  or  lefs  degree  of  feeling,  in  proportion  as  they 
are  fupplied  with  a greater  or  fmallcr  number  of  nerves. 
Upon  this  principle  it  is,  that  the  Ikin,  mnlcles,  ftomach, 
inteftines,  urinary  bladder,  ureters,  uterus,  vagina,  penis, 
tongue,  and  retina,  are  extremely  fenfiblc,  while  the  lungs 
and  glands  have  only  an  oblcure  degree  of  feelingr 


4o8 


OF  THE  SENSES 


Part  VI. 


Sect.  II.  Of  the  Tafe. 

The  fenfe  of  tafte  is  feated  chiefly  in  the 
tongue ; the  fituation  and  figure  of  which  are 
fufliciently  known. 

On  the  upper  furface  of  this  organ  we  may 
obferve  a great  number  of  papillae,  which,  on 
account  of  their  difference  in  fize  and  fhape, 
are  commonly  divided  into  three  claffes.  The 
largefl;  are  fituated  towards  the  bafis  of  the 
tongue.  Their  number  commonly  varies  from 
feven  to  nine,  and  they  feem  to  be  mucous  fol- 
licles. Thofe  of  the  fecond  clafs  are  fomewhat 
fmaller,  and  of  a cylindrical  fhape.  They  are 
moft  numerous  about  the  middle  of  the  tongue. 
Thofe  of  the  third  clafs  are  very  minute,  and  of 
a conical  fhape.  They  are  very  numerous  on 
the  apex  and  edges  of  the  tongue,  and  have  been 
fuppofed  to  be  formed  by  the  extremities  of  its 
nerves. 

We  obferve  a line,  the  linea  lingua  mediana^ 
running  along  the  middle  of  the  tongue,  and  di- 
viding it  as  it  were  into  portions.  Towards  the 
bafis  of  the  tongue,  we  meet  with  a little  cavity, 
named  by  Morgagni  foramen  c cecum ^ which 
feems  to  be  nothing  more  than  a common  termi- 
nation of  fome  of  the  excretory  du£ts  of  mu- 
cous glands  fituated  within  the  fubftance  of  the 
tongue. 


We 


Part  VI.  AND  THEIR  ORGANS.  409 

We  have  already  obferved,  that  this  organ  is 
every  where  covered  by  the  cuticle,  which,  by 
forming  a reduplication,  called  the  franum^  at 
its  under  part,  ferves  to  prevent  the  too  great 
motion  of  the  tongue,  and  to  fix  in  it  its  fituation. 
But,  befides  this  attachment,  the  tongue  is  con- 
nected by  means  of  its  mufcles  and  membranou?' 
ligaments,  to  the  lower  jaw,  the  os  hyoides,  and 
the  ftyloid  proceffes. 

The  principal  arteries  of  the  tongue  are  the 
linguales,  which  arife  from  the  external  carotid. 
Its  veins  empty  themfelves  into  the  external  ju- 
gulars. Its  nerves  arife  from  the  fifth,  eighth, 
and  ninth,  pair. 

The  variety  of  taftes  feems  to  be  occafioned 
by  the  different  impreffions  made  on  the  papil- 
Ise  by  the  food.  The  different  Rate  of  the  pa- 
pilla with  refped  to  their  moifture,  their  figure, 
or  their  covering,  feems  to  produce  a confidera- 
ble  difference  in  the  tafte,  not  only  in  diffe- 
rent people,  but  in  the  fame  fubjeCt,  in  ficknefs 
and  in  health.  The  great  ufe  of  the  tafte  feems 
to  be  to  enable  us  to  diftinguifh  wholefome  and 
falutary  food  from  that  which  is  unhealthy  ; 
and  we  obferve  that  many  quadrupeds,  by  hav- 
ing their  papilla  (u)  very  large  and  long,  have 

the 

(u)  Malpighi’s  defcription  of  the  papillse,  which  has  been 
cepied  by  many  anatomical  writers,  feems  to  have  been 
taken  chiefly  front  the  tongues  of  fleep. 


410  OF  THE  SENSES  Part  VI. 

the  faculty  of  diftinguifhing  flavours  with  infi- 
nite accuracy. 

Sect  III.  Of  fmelling. 

The  fenfe  of  fmelling,  like  the  fenfe  of  tafte, 
feems  intended  to  dired;  us  to  a proper  choice  of 
aliment,  and  is  chiefly  feated  in  the  nofe,  which 
is  diftinguiflied  into  its  external  and  internal  parts. 
The  fituation  and  figure  of  the  former  of  thefe 
do  not  feem  to  require  a definition.  It  is  compof- 
ed  of  bones  and  cartilages,  covered  by  mufcu- 
lar  fibres  and  by  the  common  teguments.  The 
bones  make  up  the  upper  portion,  and  the  car- 
tilages the  lower  one.  The  feptum  narium, 
like  the  nofe,  is  likewife  in  part  bony,  and  in 
part  cartilaginous.  Thefe  bones  and  their  con- 
nexions were  defcribed  in  the  ofteology. 

The  internal  part  of  the  nofe,  befides  the  olTa 
fpongiofa,  has  fix  cavities  or  finufes,  the  max- 
illary, the  frontal,  and  the  fphenoid,  which  were 
all  defcribed  with  the  bones  of  the  head.  They 
all  open  into  the  noftrils ; and  the  nofe  likewife 
communicates  with  the  mouth,  larynx,  and 
pharynx,  pofteriorly  behind  the  velum  palati. 

All  thefe  feveral  parts,  which  are  included  in 
the  internal  divifion  of  the  nofe,  viz.  the  inner 
furface  of  the  noftrils,  the  lamellae  of  the  olTa 
fpongiofa,  and  the  finufes,  are  lined  by  a very 
vafcular  membrane,  which  though  not  unknown 
to  the  ancients,  was  firft  well  defcribed  by 

Schneider 


PartVI.'^  and  their  organs.  41 1 

Schneider  and  is  therefore  now  commonly 
named  memhrana  pituitaria  Schneideri.  This 
membrane  is  truly  the  organ  of  fmelling ; but 
its  real  ftrudture  does  not  yet  feem  to  be  perfect- 
ly uriderftood.  It  appears  to  be  a continuation 
of  the  cuticle,  which  lines  the  inner  furface  of 
the  mouth.  In  fome  parts  of  the  nofe  it  is 
fmooth  and  firm,  and  in  others  it  is  loofe  and 
fpongy.  It  is  conftantly  moiltened  by  a mu- 
cous fecretion  ; the  finer  parts  of  which  are 
carried  off  by  the  air  we  breathe,  and  the  re- 
mainder, by  being  retained  in  the  fmufes,  ac- 
quires confiderable  confiftence.  The  manner  in 
which  this  mucus  is  fecreted  has  not  yet  been  fa- 
tisfaCtorily  afcertained ; but  it  feems  to  be  by 
means  of  mucous  follicles. 

Its  arteries  are  branches  of  the  internal  max- 
illary and  internal  carotid.  Its  veins  empty 
themfelves  into  the  internal  jugulars.  The  firfl 
pair  of  nerves,  the  olfaCtory,  are  fpread  over 
every  part  of  it,  and  it  likewife  receives  branches 
from  the  fifth  pair. 

After  what  has  been  faid  of  the  pituitary  mem- 
brane, it  will  not  be  difficult  to  conceive  how 
the  air  we  draw  in  at  the  noftrils,  being  im- 
pregnated with  the  effluvia  of  bodies,  excites  in 
us  that  kind  of  fenfation  we  call  fmdUng.  As 
thefe  effluvia,  from  their  being  exceedingly 
light  and  volatile,  cannot  be  capable  in  a fmall 

quantity 


DeCatarrho,  lib.  iii. 


41 2 OF  THE  SENSES  Part  VI. 

quantity  of  making  any  great  impreflion  on  the 
extremities  of  the  olfactory  nerves,  it  was  ne- 
ceffary  to  give  confiderable  extent  to  the  pituitary 
membrane,  that  by  this  means  a greater  num- 
ber of  odoriferous  particles  might  be  admitted 
at  the  fame  time.  When  we  wifh  to  take  in 
much  of  the  effluvia  of  any  thing,  we  naturally 
clofe  the  mouth,  that  all  the  air  we  infpire  may 
pafs  through  the  noftrils  ; and  at  the  fame  time, 
by  means  of  the  mufcles  of  the  nofe,  the  nof- 
trils are  dilated,  and  a greater  quantity  of  air 
is  drawn  into  them. 

In  many  quadrupeds,  the  fenfe  of  fmelling 
is  much  more  extenlive  and  delicate  than  it  is  in 
the  human  fubjed; ; and  in  the  human  fubjed  it 
feems  to  be  more  perfed  the  lefs  it  is  vitiated  by 
a variety  of  fmells.  It  is  not  always  in  the 
fame  ftate  of  perfedion,  being  naturally  affed- 
ed  by  every  change  of  the  pituitary  membrane, 
and  of  the  lymph  with  which  that  membrane  is 
moiftened. 

Sect.  IV.  Of  Hearing. 

Before  we  undertake  to  explain  the  manner 
in  which  we  are  enabled  to  receive  the  impreffi- 
ons  of  found,  it  will  be  neceffary  to  defcribe  the 
which  is  the  organ  of  hearing.  It  is  com- 
monly diftinguifhed  into  external  and  internal, 
The  former  of  thefe  divifions  includes  all  that 
we  are  able  to  difcover  without  diffedion,  and 

the 


Part  VI.  AND  THEIR  ORGANS  413 
the  meatus  auditorius,  as  far  as  the  typanum ; 
and  the  latter,  all  the  other  parts  of  the  ear. 

The  external  ear  is  a cartilaginous  funnel  co- 
vered by  the  common  integuments,  and  attach- 
ed by  means  of  its  ligaments  and  mufcles,  to 
the  temporal  bone.  Although  capable  only  of 
a very  obfcure  motion,  it  is  found  to  have  feve- 
ral  ^pufcles.  Different  parts  of  it  are  diftinguilh- 
ed  by  feveral  names ; all  its  cartilaginous  part  is 
called  ala  or  w'lng^  to  diftinguifh  it  from  the 
foft  and  pendent  part  below,  called  the  lobe.  Its 
outer  circle  or  border  is  called  helix.^  and  the  fe- 
micircle  within  this,  atitibelix.  The  moveable 
cartHage  placed  immediately  before  the  meatus 
auditorius,  which  it  may  be  made  to  clofe  ex- 
actly, is  named  tragus ; and  an  eminence  op- 
pofite  to  this  at  the  extremity  of  the  antihelix, 
is  called  antitragus.  The  concha  is  a confider- 
able  cavity  formed  by  the  extremities  of  the  he- 
lix and  antihelix.'  The  meatus  auditorius, 
which  at  its  opening  is  cartilaginous,  is  lined 
with  a very  thin  membrane,  which  is  a conti- 
nuation of  the  cuticle  from  the  furface  of  the 
ear. 

In  this  canal  we  find  a yellow  wax,  which  is 
fecreted  by  a number  of  minute  glands  or  folli- 
cles, each  of  which  has  an  excretory  dufi:.  This 
fecretion;  which  is  at  firft  of  an  oily  confiftence, 
defends  the  membrane  of  the  typanum  from  the 
injuries  of  the  air  ; and  by  its  bitternefs,  pre- 
vents minute  infeds  from  entering  into  the  ear. 

But 


41 4 OF  THE  SENSES  Part  VI. 

But  when  from  negleS:  or  difeafe  it  accumulates 
in  too  great  a quantity,  it  fometimes  occafions 
deafnefs.  The  inner  extremity  of  the  meatus  is 
clofed  by  a ver^:^  thin  traidpai  ent  membrane,  the 
membrana  tympani,  which  is  fet  in  a bony  cir- 
cle like  the  head  of  a dnini.  In  the  laft  century 
Rivinus,  profelTor  at  Leipfic,  fancied  he  had 
difcovered  a hole  in  this  membrane,  furrounded 
by  a fphindter,  and  affording  a paffage  to  the 
air,  between  the  external  and  internal  ear.  Cow- 
per,  Heifter,  and  fome  other  anatomifts,  have 
admitted  this  fuppofed  foramen,  which  certain- 
ly does  not  exift.  Whenever  there  is  any  open- 
ing in  the  membrana  tympani,  it  may  be  confi- 
dered  as  accidental.  Under  the  membrana  tym- 
pani runs  a branch  of  the  fifth  pair  of  the  nerves, 
called  chorda  tympani ; and  beyond  this  mem- 
brane is  the  cavity  of  the  tympanum,  which  is 
about  feven  or  eight  lines  wide,  and  half  fo  ma- 
ny in  depth ; it  is  femifplierical,  and  every 
where  lined  by  a very  fine  membrane.  There 
are  four  openings  to  be  obferved  in  this  cavity. 
It  communicates  with  the  mouth  by  means  of 
the  Euhachian  tube.  This  canal,  which  is  in 
part  bony  and  in  part  cartilaginous,  begins  by  a 
very  narrow  opening  at  the  anterior  and  almoft 
fuperior  part  of  the  tympanum,  increafmg  in 
fize  as  it  advances  towards  the  palate  of  the 
mouth,  where  it  terminates  by  an  oval  opening. 
This  tube  is  every  where  lined  by  the  fame  mem- 
brane that  covers  the  infide  of  the  mouth.  The 

real 


Part  VI.  AND  THEIR  ORGANS.  41 5 
real  ufe  of  this  canal  does  notfeem  to  have  been 
hitherto  fatisfadlorily  afcertained  ; but  found 
would  feem  to  be  conveyed  through  it  to  the 
membrana  tympani,  deaf  perfons  being  often 
obferved  to  liften  attentively  with  their  mouths 
open.  Oppofite  to  this  is  a minute  palTage, 
which  leads  to  the  fmuofities  of  the  maftoid  pro- 
cefs  ; and  the  two  other  openings,  which  are  in 
the  internal  procefs  of  the  os  petrofum,  are  the 
feneftra  ovalis,  and  feneftra  rotunda,  both  of 
which  are  covered  by  a very  fine  membrane. 

There  are  three  diftin£t  bones  in  the  cavity 
of  the  tympanum ; and  thefe  are  the  malleus, 
incus,  and  Rapes.  Befides  thefe  there  is  a fourth, 
which  is  the  os  orbiculare^  confidered  by  fome 
anatomifts  as  a procefs  of  the  Rapes,  which  is 
neceffarily  broken  off  by  the  violence  we  are 
obliged  to  ufe  in  getting  at  thefe  bones  ; but 
when  accurately  confidered,  it  feems  to  be  a 
diRinft  bone. 

The  malleus  is  fuppofed  to  refemble  a ham- 
mer, being  larger  at  one  extremity,  which  is  its 
head,  than  it  is  at  the  other,  which  is  its  han- 
dle. The  latter  is  attached  to  the  membrana 
tympani,  and  the  head  of  the  bone  is  articulat- 
ed with  the  incus. 

The  incus ^ as  it  is  called  from  its  fhape,  though 
it  feems  to  have  lefs  refemblance  to  an  anvil  than 
to  one  of  the  dentes  molares  with  its  roots  wide- 
ly feparated  from  each  other,  is  diRinguifhed  in- 
to its  body  and  its  legs.  One  of  its  legs  is  plac- 


4i6  of  the  senses  Part  VI. 

ed  at  the  entry  of  the  canal  which  leads  to  the 
maftoid  procefs  ; and  the  other,  which  is  fome- 
what  longer,  is  articulated  with  the  ftapes,  or 
rather  with  the  os  orbiculare,  which  is  placed 
between  them. 

The  third  bone  is  very  properly  named Jiapes^ 
being  perfectly  fhaped  like  a ftirrup.  Its  bafis 
is  fixed  into  the  feneftra  ovalis,  and  its  upper 
part  is  articulated  with  the  os  orbiculare.  What 
is  called  the  fenejl7'a  rotunda^  though  perhaps 
improperly,  as  it  is  more  oval  than  round,  is 
obferved  a little  above  the  other,  in  an  emi- 
nence formed  by  the  os  petrofum,  and  is  clofed 
by  a continuation  of  the  membrane  that  lines 
the  inner  furface  of  the  tympanum.  The 
ftapes  and  malleus  are  each  of  them  furniftied 
with  a little  mufcle,  the  ftapedeus  and  tenfor  tym- 
pani.  The  firft  of  thefe,  which  is  the  fmalleft  in 
the  body,  arifes  from  a little  cavern  in  the  pof- 
terior  and  upper  part  of  the  cavity  of  the  tym- 
panum ; and  its  tendon,  after  pafling  through 
a hole  in  the  fame  cavern,  is  inferted  at  the 
back  part  of  the  head  of  the  ftapes.  This  mufj 
cle,  by  drawing  the  ftapes  obliquely  upwards,  af- 
fifts  in  ftretching  the  membrana  tympani. 

The  tenfor  tympani  (x,)  or  internus  malei, 
as  it  is  called  by  fome  writers,  arifes  from  the 

carti- 

(x)  Some  anatom’ifts  defcribe  three  mufcles  of  the  mal- 
leus : but  only  this  onefeems  to  deferve  the  name  of  mufcle; 
what  are  called  the  externus  and  obliquus  molleif  feeming  to 
be  ligaments  rather  than  mufcles. 


Part  VI.  AND  THEIR  ORGANS.  417 
cartilaginous  extremity  of  the  Euftachian  tube, 
and  is  inferted  into  the  back  part  of  the  handle 
of  the  malleus,  which  it  ferves  to  pull  inwards, 
and  of  courfe  helps  to  flretch  the  membrana  tym- 
pani. 

The  labyrinth  is  the  only  part  of  the  ear  which 
remains  to  be  defcribed.  It  is  fituated  in  the  os 
petrofum,  and  is  feparated  from  the  tympanum 
by  a partition  which  is  every  where  bony,  except 
at  the  two  feneftrae.  It  is  compofed  of  three 
parts  ; and  thefe  are  the  veftibulum,  the  femicir- 
cular  canals,  and  the  cochlea. 

The  vejiibulum  is  an  irregular  cavity,  much 
fmaller  than  the  tympanum,  fituated  nearly  in 
the  centre  of  the  os  petrofum,  between  the  tym- 
panum, the  cochlea,  and  the  femicircular  canals. 
It  is  open  on  the  fide  of  the  tympanum  by  means- 
of  the  feneftra  ovalis,  and  communicates  with 
the  upper  portion  of  the  cochlea  by  an  oblong- 
foramen,  which  is  under  the  feneftra  ovalis,  from 
which  it  is  feparated  only  by  a very  thin  parti- 
tion. 

Each  of  the  three  femicircular  canals  forms 
about  half  a circle  of  nearly  a line  in  diameter, 
and  running  each  in  a different  direflion,  they 
are  diftinguifhed  into  vertical^  oblique^  and  hot'i- 
%ontal.  Thefe  three  canals  open  by  both  their 
extremities  into  the  veftibulum  ; but  the  vertical 
and  the  oblique  being  united  together  at  one  of 
their  extremities,  there  are  only  five  orifices  to  be 
feen  in  the  veftibulum. 

Dd 


The 


41 8 OF  THE  SENSES  Part  VI. 

The  cochlea  is  a canal  which  takes  a fpiral 
courfe,  not  unlike  the  fhell  of  a fnail.  From  its 
bafis  to  its  apex  it  makes  two  turns  and  a half ; 
and  is  divided  into  two  canals  by  a very  thin  la- 
mina or  feptum,  which  is  in  part  bony  and  in 
part  membranous,  in  fuch  a manner  that  thefe 
two  canals  only  communicate  with  each  other  at 
the  point.  One  of  them  opens  into  the  veftibu- 
lum,  and  the  other  is  covered  by  the  membrane 
that  clofes  the  feneftra  rotunda.  The  bony  la- 
mella which  feparates  the  two  canals  is  exceed- 
ingly thin,  and  fills  about  two  thirds  of  the  dia- 
meter of  the  canal.  The  reft  of  the  feptum  is 
compofed  of  a moft  delicate  membrane,  which 
lines  the  whole  inner  furface  of  the  cochlea,  and 
feems  to  form  this  divifion  in  the  fame  man- 
ner as  the  two  membranous  bags  of  the  pleura, 
by  being  applied  to  each  other,  form  the  mediaf- 
tinum. 

Every  part  of  the  labyrinth  is  furniftied  with 
a very  delicate  periofteum,  and  filled  with  a wa- 
tery fluid,  fecreted  as  in  other  cavities.  This 
fluid  tranfmits  to  the  nerves  the  vibrations  it  re- 
ceives from  the  membrane  clofing  the  feneftra  ro- 
tunda, and  from  the  bafis  of  the  ftapes,  where 
it  refts  on  the  feneftrum  ovale.  When  this  fluid 
is  colledfed  in  too  great  quantity,  or  is  comprefled 
by  the  ftapes,  it  is  fuppofed  to  efcape  through 
two  minute  canals  or  aqueducts,  lately  defcribed 


Part  VI.  AND  THEIR  ORGANS.  419 
by  Dr  Cotunni  an  ingenious  phyfician  at  Na- 
ples. One  of  thefe  aqueducts  opens  into  the 
bottom  of  the  veftibulum,  and  the  other  into 
the  cochlea,  near  the  feneftra  rotunda.  They 
both  pafs  through  the  os  petrofum,  and  com- 
municate with  the  cavity  of  the  cranium  where 
the  fluid  that  paflTes  through  them  is  abforbed  ; 
and  they  are  lined  by  a membrane  which  is  fup- 
pofed  to  be  a production  of  the  dura  mater. 

The  arteries  of  the  external  ear  come  from 
the  temporal  and  other  branches  of  the  external 
carotid,  and  its  veins  pafs  into  the  jugular.  The 
internal  ear  receives  branches  of  arteries  from  the 
bafilary  and  carotids,  and  its  veins  empty  them- 
felves  into  the  finufes  of  the  dura  mater,  and  into 
the  internal  jugular. 

The  portio  mollis  of  the  feventh  pair  is 
diftributed  through  the  cochlea,  the  veftibu- 
lum, and  the  femi-circular  canals  ; and  the 
portio  dura  fends  off  a branch  to  the  tympa- 
num, and  other  branches  to  the  external  ear  and 
parts  near  it. 

The  Jenfe  of  hearings  in  producing  which  all 
the  parts  we  have  delcribed  aflift,  is  occafioned 
by  a certain  modulation  of  the  air  collected  by  the 
funnel-like  flhiape  of  the  external  ear,  and  con- 
veyed through  the  meatus  auditorius  to  the  mem- 
brana  tympani.  That  found  is  propagated  by- 
means  of  the  air,  is  very  eafily  proved  by  ring- 
D d 2 ing 


*-  De  aquxduCtibus  Auris  Humanse  Interns,  8vc,  176a. 


420  OF  THE  SENSES  Part  VL 

ing  a bell  under  the  receiver  of  an  air-pump  ; 
the  found  it  affords  being  found  to  diminifh  gra- 
dually as  the  air  becomes  exhaufled,  till  at  length 
it  ceafes  to  be  heard  at  all.  Sound  moves  through 
the  air  with  infinite  velocity ; but  the  degree  of 
its  motion  feems  to  depend  on  the  ftate  of  the 
rdf,  as  it  conftantly  moves  fafter  in  a denfe  and 
dry,  than  it  does  in  a moifl  and  rarefied  air.  See 
Acoujlics^  n^  20. 

That  the  air  vibrating  on  the  membrana  tym- 
pani  communicates  its  vibration  to  the  different 
parts  of  the  labyrinth,  and  by  means  of  the 
fluid  contained  in  this  cavity  affedts  the  auditory 
nerve  fo  as  to  produce  found,  feems  to  be  very 
probable  : but  the  fituation,  the  minutenefs,  and 
the  variety  of  the  parts  which  compofe  the  ear, 
do  not  permit  much  to  be  advanced  with  certain- 
ty concerning  their  mode  of  addon. 

Some  of  thefe  parts  feem  to  conftitute  the  im- 
mediate organ  of  hearing,  and  thefe  are  all  the 
parts  of  the  veftibulum  : but  there  are  others 
which  feem  intended  for  the  perfedtion  of  this 
fenfe,  without  being  abfolutely  effential  to  it.  It 
has  happened,  for  inflance,  that  the  membrana 
tympani,  and  the  little  bones  of  the  ear,  have 
been  deftroyed  by  difeafe,  without  depriving  the 
patient  of  the  fenfe  of  hearing  (y). 

Sound 

(y)  This  obfervation  has  led  to  a fuppofitlon,  that  a per- 
foration of  this  membrane  may  in  fome  cafes  of  deafnefs  be 
vifeful;.  and  Mr.  Cheielden  relates,  that,  fome  years' ago,  a 


Part  VI.  AND  THEIR  ORGANS.  42 1 

Sound  is  more  or  lefs  loud  in  proportion  to 
the  ftrength  of  the  vibration  ; and  the  variety 
of  founds  feems  to  depend  on  the  difference  of 
this  vibration  ; for  the  more  quick  and  frequent 
it  is,  the  more  acute  will  be  the  found,  and  vice 
verfa. 

Before  we  conclude  this  article,  it  will  be 
right  to  explain  certain  phenomena,  which 
will  be  found  to  have  a relation  to  the  organ  of 
hearing. 

Every  body  has,  in  confequence  of  particular 
founds,  occafionally  felt  that  difagreeable  fenfa- 
tion  which  is  ufually  called  Jetting  the  teeth  on 
edge  : and  the  caufe  of  this  fenfation  may  be 
traced  to  the  communication  which  the  portio 
dura  of  the  auditory  nerve  has  with  the  branches 
of  the  fifth  pair  that  are  diftributed  to  the  teeth, 
being  probably  occafioned  by  the  violent  tremor 
produced  in  the  membrana  tympani  by  thefe  ve- 
ry acute  founds.  Upon  the  fame  principle  we 
may  explain  the  ftrong  idea  of  found  which  a 
perfon  has  who  holds  a vibrating  firing  between 
his  teeth. 

The  humming  which  is  fometimes  perceived 
in  the  ear,  without  any  exterior  caufe,  may  be 
occafioned  either  by  an  increafed  adtion  of  the 
arteries  in  the  ears,  or  by  convulfive  contractions 

of 

malefaftor  was  pardoned  on  condition  that  he  flaould  fiibinit 
to  this  operation  ; but  the  public  clamour  railed  againfl;  it 
was  fo  great,  that  it  was  thought  right  not  to  perform  it. 


422  OF  THE  SENSES  Part  VI. 

of  the  mufcles  of  the  malleus  and  ftapes,  affecting 
the  auditory  nerve  in  fuch  a manner  as  to  produce 
the  idea  of  found.  An  ingenious  philofophical 
writer  * has  lately  difcovered,  that  there  are 
founds  liable  to  be  excited  in  the  ear  by  irritation, 
and  without  any  alTiftance  from  the  vibrations  of 
the  air. 

Sect.  V.  Of  Vifion. 

The  eyes,  which  conftitute  the  organ  of  vi- 
fion,  are  fituated  in  two  bony  cavities  named 
orbits^  where  they  are  furrounded  by  feveral 
parts,  which  are  either  intended  to  protedf 
them  from  external  injury,  or  to  ailift  in  their 
motion. 

The  globe  of  the  eye  is  immediately  covered 
by  two  eye-lids  or  palpebrse,  which  are  compof- 
ed  of  mufcular  fibres  covered  by  the  common  in- 
teguments, and  lined  by  a very  fine  and  fmooth 
membrane,  which  is  from  thence  extended  over 
pan  of  the  globe  of  the  eye,  and  is  called  tunica 
conjunBiva.  Each  eye-lid  is  cartilaginous  at  its 
edge  ; and  this  border  which  is  called  tarfus,  is 
furnifhed  with  a row  of  hairs  named  cilia  or  eye- 
lafdcs. 

The 

* Elliot’s  Philofophical  Obfervations  on  the  Senfes  of  Yj- 
fion  and  Hearing,  bvo. 


Part  VI.  AND  THEIR  ORGANS.  423 

The  cilia  ferve  to  protect  the  eye  from  infers 
and  minute  bodies  floating  in  the  air,  and  like- 
wife  to  moderate  the  action  of  the  rays  of  light 
in  their  paflage  to  the  retina.  At  the  roots  of 
thefe  hairs  there  are  febaceous  follicles,  firfl:  No- 
ticed by  Meibomius,  which  difcharge  a glutinous 
liniment.  Sometimes  the  fluid  they  fecrete  has 
too  much  vifcidity,  and  the  eye-lids  become 
glued  to  each  other. 

The  upper  border  of  the  orbit  is  covered  by 
the  eye-brows  or  fupercilia,  which  by  means  of 
their  two  mufcles  are  capable  of  being  brought 
towards  each  other,  or  of  being  carried  upwards. 
They  have  been  confidered  as  ferving  to  protect 
the  eyes,  but  they  are  probably  intended  more  for 
ornament  than  utility  (z). 

The  orbits,  in  which  the  eyes  are  placed,  are 
furnifhed  with  a good  deal  of  fat,  which  affords 
a foft  bed  on  which  the  eye  performs  its  feveral 
motions.  The  inner  angle  of  each  orbit,  or  that 
part  of  it  which  is  near  the  nofe,  is  called  canthus 
major ^ or  the  great  angle  ; and  the  outer  angle, 
which  is  on  the  oppofite  fide  of  the  eye,  is  the 
canthus  minor ^ or  little  angle. 

The  little  reddifli  body  which  we  obferve  in 
the  great  angle  of  the  eye-lids,  and  which  is  call- 
ed caruncula  lachrymalis.^  is  fuppofed  to  be  of  a 
glandular  ftru£lure,  and,  like  the  follicles  of  the 

eye-r 

(z)  It  is  obfervable,  that  the  eye-brows  are  peculiar  to  the 
Tiuman  fpecies. 


424  OF  THE  SENSES  Part  VI. 

eye-lids,  to  fecrete  an  oily  humour.  But  its 
ftrud:ure  and  ufe  do  not  feein  to  have  been  hi- 
therto accurately  determined.  The  furface  of  the 
eye  is  conftantly  moiftened  by  a very  fine  limpid 
fluid  called  the  tears ^ which  is  chiefly,  and  per- 
haps wholly,  derived  from  a large  gland  of  the 
conglomerate  kind,  fituated  in  a fmall  depreflion 
of  the  os  frontis  near  the  outer  angle  of  the  eye. 
Its  excretory  dudls  pierce  the  tunica  conjunctiva 
juft  above  the  cartilaginous  borders  of  the  upper 
eye-lids.  When  the  tears  were  fuppofed  to  be 
fecreted  by  the  caruncule,  this  gland  was  called 
giandula  innoyninata ; but  now  that  its  ftructure 
and  ufes  arc  afeertained,  it  very  properly  has  the 
name  of  glandula  lachrymalis.  The  tears  pour- 
ed out  by  the  ducts  of  this  gland  are,  in  a natu- 
ral and  healthy  ftate,  incefiantly  fpread  over  the 
furface  of  the  eye,  to  keep  it  clear  and  tranfpa- 
rent,  by  means  of  the  eye-lids,  and  as  conftantly 
pafs  out  at  the  oppofite  corner  of  the  eye  or  in- 
ner ^nglc,  through  tw^o  minute  orifices,  thepunc- 
ta  lachrymalia  (a)  ; being  determined  into  thefe 
little  openings  by  a duplication  of  the  tunica  con- 
junctiva, fhaped  like  a crefeent,  the  two  points 
of  which  anfwer  to  the  puncta  This  reduplica- 
tion is  named  memhrana^  or  valvula  femilunaris. 

Each 

(a)  It  fometimes  happens,  that  this  very  pellucid  fluid, 
which  moiftens  the  eye,  being  poured  out  through  the  ex- 
cretory dufts  of  the  lachrymal  gland  fafter  than  it  can  be 
carried  off  through  the  pundta,  triddes  down  the  cheek, 
and  is  then  ftriftly  and  properly  called  tears. 


Part  VI.  AND  THEIR  ORGANS.  425 
Each  of  thefe  punda  is  the  beginning  of  a fmall 
excretory  tube,  through  which  the  tears  pafs  into 
a little  pouch  or  refervoir,  the  facculus  lachryma- 
lis,  which  lies  in  an  excavation  formed  partly  by 
the  nafal  procefs  of  the  os  maxillare  fuperius, 
and  partly  by  the  os  unguis.  The  lower  part  of 
this  fac  forms  a dud  called  the  duBiis  ad  nares^ 
which  is  continued  through  a bony  channel,  and 
opens  into  the  nofe,  through  which  the  tears  are 
occafionally  difcharged  (b). 

The  motions  of  the  eye  are  performed  by  fix 
mufcles : four  of  which  are  ftraight  and  two 
oblique.  The  ftraight  mufcles  are  diftinguiftied 
by  the  names  of  elevator  ^ deprejfor^  adductor^  and 
abduBor^  from  their  feveral  ufes  in  elevating  and 
deprefling  the  eye,  drawing  it  towards  the  nofe, 
or  carrying  it  from  the  nofe  towards  the  temple. 
All  thefe  four  mufcles  arife  from  the  bottom  of 
the  orbit,  and  are  inferted  by  fiat  tendons  into 
the  globe  of  the  eye.  The  oblique  mufcles  are 
intended  for  the  more  compound  motions  of  the 
eye.  The  firft  of  thefe  mufcles,  the  obliquus 
fuperior,  does  not,  like  the  other  four  mufcles 
we  have  defcribed,  arife  from  the  bottom  of  the 
orbit,  but  from  the  edge  of  the  foramen  that 
tranfmits  the  optic  nerve,  which  feparates  the 

origin 

(e)  When  the  duftns  ad  nares  becomes  obltrucled  in  con- 
fequence  of  difeafe,  the  tears  are  no  longer  able  to  pafs  into 
the  noftrils ; the  facculus  lachryinalis  becomes  dillended  ; 
and  inflammation,  and  fometimes  ulceration,  taking  place, 
conflitute  the  difeafe  called  fijlula  lachrymaiis.  • 


426  OF  THE  SENSES  Part  VI. 

origin  of  this  mufcle  from  that  of  the  others. 
From  this  beginning  it  paffes  in  a ftraight  line 
towards  a very  fmall  cartilaginous  ring,  the  fitu- 
ation  of  which  is  marked  in  the  fkeleton  by  a 
little  hollow  in  the  internal  orbitar  procefs  of  the 
os  frontis.  The  tendon  of  the  mufcle,  after 
palling  through  this  ring,  is  inferted  into  the  up- 
per part  of  the  globe  of  the  eye,  which  it  ferves 
to  draw  forwards,  at  the  fame  time  turning  the 
pupil  downwards. 

The  obliquus  inferior  arifes  from  the  edge  of 
the  orbit,  under  the  opening  of  the  du£tus  lach- 
rymalis  ; and  is  inferted  fomewhat  pofteriorly 
into  the  outer  fide  of  the  globe,  ferving  to  draw 
the  eye  forwards  and  turn  the  pupil  upwards, 
When  either  of  thefe  two  mufcles  afts  feparately, 
the  eye  is  moved  on  its  axis  ; but  when  they  a£t 
together,  it  is  comprelTed  both  above  and  below. 
The  eye  itfelf,  which  is  now  to  be  defcribed, 
with  its  tunics,  humours,  and  component  parts, 
is  nearly  of  a fpherical  figure.  Of  its  tunics,  tho 
conjunctiva  has  been  already  defcribed  as  a par- 
tial covering,  refledled  from  the  inner  furface  of 
the  eye-lids  over  the  anterior  portion  of  the  eye. 
What  has  been  named  albuginea  cannot  pro- 
perly be  confidered  as  a coat  of  the  eye,  being 
in  fadt  nothing  more  than  the  tendons  of  the 
ftraight  mufcles  fpread  over  fome  parts  of  the 
fclerotica. 

The  immediate  tunics  of  the  eye,  which  are 
to  be  demonftrated  when  its  partial  coverings, 

and 


Part  VI.  AND  THEIR  ORGANS.  427 
and  all  the  other  parts  with  which  it  is  furround- 
ed,  are  removed,  are  the  fclerotica,  cornea,  cho- 
roides,  and  retina. 

The fclerotica^  which  is  the  exterior  coat,  is 
every  where  white  and  opaque,  and  is  joined  at 
its  anterior  edge  to  another,  which  has  more 
convexity  than  any  other  part  of  the  globe,  and 
being  exceedingly  tranfparent  is  called  cornea  (c). 
Thefe  two  parts  are  perfedlly  different  in  their 
ftrufture ; fo  that  fome  anatomifts  fuppofe  them 
to  be  as  diftindl;  from  each  other  as  the  glafs  of 
a watch  is  from  the  cafe  into  which  it  is  fixed. 
The  fclerotica  is  of  a compadl  fibrous  ftrudture  ; 
the  cornea,  on  the  other  hand,  is  compofed  of  a 
great  number  of  lamina  united  by  cellular  mem- 
brane. By  macerating  them  in  boiling  water, 
they  do  not  feparate  from  each  other,  as  fome 
writers  have  afferted  ; but  the  cornea  foon  foft- 
ens,  and  becomes  of  a glutinous  confiftence. 

The  ancients  fuppofed  the  fclerotica  to  be  a 
continuation  of  the  dura  mater.  Morgagni  and 
fome  other  modern  writers  are  of  the  fame  opi- 
nion ; but  this  point  is  difputed  by  Winflow, 
Haller,  Zin,  and  others.  The  truth  feems  to 
be,  that  the  fclerotica,  though  not  a production 
of  the  dura  mater,  adheres  intimately  to  that 
membrane. 

The 

(c)  Some  writers,  who  have  given  the  name  of  cornea  to 
all  this  outer  coat,  have  named  what  is  here  and  moft  com- 
monly called  fclerotica^  cornea  opaca ; and  its  anterior  and 
tranfparent  portion,  cornea  lucida. 


428  OF  THE  SENSES  Part  VI. 

The  cboroides  is  fo  called  becaufe  it  is  furnifli- 
cd  with  a great  number  of  veffels.  It  has  like- 
wife  been  named  uvea^  on  account  of  its  refem- 
blance  to  a grape.  Many  modern  anatomical 
writers  have  confidered  it  as  a produdtion  of  the 
pia  mater.  This  was  likewife  the  opinion  of  the 
ancients  ; but  the  ftrength  and  thicknefs  of  the 
choroides,  when  compared  with  the  delicate 
ftrudture  of  the  pia  mater,  are  fulhcient  proofs  of 
their  being  two  diftind:  membranes. 

The  choroides  has  of  late  generally  been  de>* 
feribed  as  confifting  of  two  laminse  ; the  inner- 
moft  of  which  has  been  named  after  Ruyfch,  who 
firft  deferibed  it.  It  is  certain,  however,  that 
Ruyfeh’s  diftindion  is  ill  founded,  at  leaft  with 
refped  to  the  human  eye,  in  which  we  are  una- 
ble to  demonftrate  any  fuch  ftrudure,  although 
the  tunica  choroides  of  fheep  and  fome  other 
quadrupeds  may  eafily  be  feparated  into  two 
layers. 

The  choroides  adheres  intimately  to  the  fcle- 
rotica  round  the  edge  of  the  cornea  ; and  at  the 
place  of  this  union,  we  may  obferve  a little 
whitilh  areola,  named  ligamentum  ciliare^  though 
it  is  not  of  a ligamentous  nature. 

They  who  fuppofe  the  choroides  to  be  com- 
pofed  of  two  laminse,  deferibe  the  external  one 
as  terminating  in  the  ligamentum  ciliare,  and  the 
internal  one  as  extending  farther  to  form  the 
iris,  v/hich  is  the  circle  we  are  able  to  diftinguihr 
through  the  cornea  : but  this  part  is  of  a very 

different 


Part  VI.  AND  THEIR  ORGANS.  429 
different  ftnidure  from  the  choroides  } fo  that 
fome  late  writers  have  perhaps  not  improperly 
confidered  the  iris  as  a diftind;  membrane.  It 
derives  its  name  from  the  variety  of  its  colours, 
and  is  perforated  in  the  middle.  This  perfora- 
tion, which  is  called  the  pupil  or  fight  of  the 
eye,  is  clofed  in  the  foetus  by  a very  thin  vafcular 
membrane.  This  membrana  pupillaris  common- 
ly difappears  about  the  feventh  month. 

On  the  under  fide  of  the  iris  we  obferve  many 
minute  fibres,  called  ciliary  procsjfies^  which  pafs 
in  radii  or  parallel  lines  from  the  circumference 
to  the  centre.  The  contradion  and  dilatation 
of  the  pupil  are  fuppofed  to  depend  on  the  ac- 
tion of  thefe  proceffes.  Some  have  confidered 
them  as  mufcular,  but  they  are  not  of  an  irritable 
nature  ; others  have  fuppofed  them  to  be  fila- 
ments of  nerves : but  their  real  ftrudure  has 
never  yet  been  clearly  afcertained. 

Befides  thefe  ciliary  proceffes,  anatomiffs  ufu- 
ally  fpeak  of  the  circular  fibres  of  the  iris,  but 
no  filch  feem  to  exift. 

The  pofterior  furface  of  the  iris,  the  ciliary 
procefl'es,  and  part  of  the  tunica  choroides,  are 
covered  by  a black  mucus  for  the  purpofes  of  ac- 
curate and  diftind  vifion  ; but  the  manner  in 
which  it  has  been  fecreted  has  not  been  deter- 
mined. 

Immediately  under  the  tunica  choroides.  we 
find  the  third  and  inner  coat,  called  the  retina^ 

which. 


430  OF  THE  SENSES  Part  VL 

which  feems  to  be  merely  an  expanfion  of  the 
pulpy  fubftance  of  the  optic  nerve,  extending  to 
the  border  of  the  cryftaline  humour. 

The  greateft  part  of  the  globe  of  the  eye, 
within  thefe  feveral  tunics,  is  filled  by  a very 
tranfparent  and  gelatinous  humour  of  confider- 
able  confiftence,  which,  from  its  fuppofed  refem- 
blance  to  fufed  glafs,  is  called  the  vitreous  humour. 
It  is  invefted  by  a very  fine  and  delicate  mem- 
brane, called  tunica  vitfea,  and  fometimes  arach- 
noides. — It  is  fuppofed  to  be  compofed  of  two 
laminae ; one  of  which  dips  into  its  fubftance, 
and  by  dividing  the  humour  into  cells  adds  to 
its  firmnefs.  The  fore-part  of  the  vitreous  hu- 
mour is  a little  hollowed,  to  receive  a very  white 
and  tranfparent  fubftance  of  a firm  texture,  and 
of  a lenticular  and  fomewhat  convex  fhape, 
named  the  cryjialine  humour.  It  is  included  in  a 
capfula,  which  feems  to  be  formed  by  a fepara- 
tion  of  the  two  laminae  of  the  tunica  vitrea. 

The  fore-part  of  the  eye  is  filled  by  a very  thin 
and  tranfparent  fluid,  named  the  aqueous  humour^ 
which  occupies  all  the  fpace  between  the  cryftal- 
line  and  the  prominent  cornea. — The  part  of  the 
choroides  which  is  called  the  /m,  and  which 
comes  forward  to  form  the  pupil,  appears  to  be 
fufpended  as  it  were  in  this  humour,  and  has  oc- 
cafioned  this  portion  of  the  eye  to  be  diftin- 
guiftied  into  two  parts.  One  of  thefe,  which  is 
the  little  fpace  between  the  anterior  furface  of 
the  cryftalline  and  the  iris,  is  called  the  pojlerior 

chamber  y 


Part  VI.  AND  THEIR  ORGANS.  431 
chamber;  and  the  other,  which  is  the  fpace 
between  the  iris  and  the  cornea,  is  called  the 
anterior  chamber  of  the  eye  (d).  Both  thele 
fpaces  are  completely  filled  with  the  aqueous 
humour,  (e). 

The  eye  receives  its  arteries  from  the  internal 
carotid  through  the  foramina  optica  j and  its 
veins  pafs  through  the  foramina  lacera,  and 
empty  themfelves  into  the  lateral  finufes.  Some 
of  the  ramifications  of  thefe  veffels  appear  on  the 
inner  furface  of  the  iris,  where  they  are  feen 
to  make  very  minute  convolutions,  which  are 
fufficiently  remarkable  to  be  diftinguifhed  by 
the  name  of  circulus  arteriofus^  though  per- 
haps improperly,  as  they  are  chiefly  branches  of 
veins. 

The 

(d)  We  are  aware  that  fome  anatomifts,  particularly  Lleu- 
taud,  are  of  opinion,  that  the  iris  is  every  where  in  ciofe 
contaft  with  the  cryftalline,  and  that  it  is  of  courfe  righf  to 
Ipeak  only  of  one  chamber  of  the  eye  ; but  as  this  does 
not  appear  to  be  the  cafe,  the  fituation  of  the  iris  and  the 
two  ciaambers  of  the  eye  are  here  defcribed  in  the  ufual 
way. 

(e)  When  the  cryftalline  becomes  opaque,  fo  as  to  pre- 
vent the  paffing  of  the  rays  of  light  to  the  retina,  it  con- 
flitutes  what  is  called  a contraEl ; and  the  operation  of 
couching  confifts  in  removing  the  difeafed  cryftalline  from 
its  bed  in  the  vitreous  huinq,ur.  In  this  operation  the  cor- 
nea is  perforateed,  and  the  aqueous  humour  elcapes  out  of 
the  eye,  but  it  is  conftantly  renewed  again  in  a very  ftiort 
time.  The  manner,  however,  in  which  it  is  fecreted,  has 
not  yef  been  determined. 


432  OF  THE  SENSES  Part  VI. 

The  optic  nerve  pafles  in  at  the  pofterior  part 
of  the  eye,  in  a confiderable  trunk,  to  be  ex- 
panded for  the  purpofes  of  vifion,  of  which  it 
is  now  univerfally  fuppofed  to  be  the  immediate 
feat.  But  Meflrs.  Mariotte  and  Mery  contend- 
ed, that  the  choroides  is  the  feat  of  this  fenfe  ; 
and  the  ancients  fuppofed  the  cryftalline  to  be 
fo.  Befides  the  optic,  the  eye  receives  branches 
from  the  third,  fourth,  fifth,  and  fixth  pair  of 
nerves. 

The  humours  of  the  eye,  together  with  the 
cornea,  are  calculated  to  refrad:  and  converge 
the  rays  of  light  in  fuch  a manner  as  to  form  at 
the  bottom  of  the  eye  a diftind  image  of  the 
objed  we  look  at ; and  the  point  where  thefe 
rays  meet  is  called  the focus  of  the  eye.  On  the 
the  retina,  as  in  the  camera  ohfcura^  the  objed 
is  painted  in  an  inverted  pofition  ; and  it  is  on- 
ly by  habit  that  we  are  enabled  to  judge  of  its 
true  fituation,  and  likewife  of  its  diftance  and 
magnitude.  To  a young  gentleman  who  was 
born  blind,  and  who  was  couched  by  Mr.  Che- 
felden,  every  objed  (as  he  expreffed  himfelf) 
feemed  to  touch  his  eyes  as  what  he  felt  did  his 
fkin  ; and  he  thought  no  objeds  fo  agreeable  as 
thofe  which  were  fmooth  and  regular,  although 
for  fome  time  he  could  form  no  judgment  of 
their  fhape,  or  guefs  what  it  was  in  any  of  them 
that  was  pleafmg  to  him. 

In  order  to  paint  objeds  diftindly  on  the  re- 
tina, the  cornea  is  required  to  have  fuch  a de- 
3 


Part  VI.  AND  THEIR  ORIGIN.  433 

gree  of  convexity,  that  the  rays  of  light  may  be 
collected  at  a certain  point,  fo  as  to  terminate 
exactly  on  the  retina-^ — If  the  cornea  is  too  pro- 
minent, the  rays,  by  diverging  too  foon,  will 
be  united  before  they  reach  the  retina,  as  is 
the  cafe  with  near-fighted  people  or  myopes  ; and 
^ on  the‘  Contrary,  if  it  is  not  fufficiently  convex, 
the  rays -will  not  be  perfectly  united  when  they 
reach  the  back  part  of  the  eye  ; and  this  hap- 
pens to  long-fighted  people  oxprejhi^  being  found 
conftantly  to  take  place  as  we  approach  to  old 
age,  when  the  eye  gradually  flattens  (f).  Thefe 
defeats  are  to  be  fupplied  by  means  of  glalTes. 
He  who  has  too  prominent  an  eye,  will  find 
his  vifion  improved  by  means  of  a concave  glafs ; 
and  upon  the  fame  principles,  a convex  glafs 
will  be  found  ufeful  to  a perfon  whofe  eye  is  na- 
turally too  flat. 

(f)  Upon  this  principle,  they  who  in  their  youth  are 
near-fighted  may  expeft  to  fee  better  as  they  advant^  in  life, 
as  their  eyes  gradually  become  more  flat.  ' 


E e 


EXPLA- 


OF  THE  SENSES 


Part  VL 


'434 

EXPLANATION  cf  PLATE  XXX. 

Figure  i.  Shows  the  Lachrymal  Canals,  after 
the  Common  Teguments  and  Bones  have  been 
cut  away. 

a,  The  lachrymal  gland,  b,  The  two  pundla 
lachrymalia,  from  which  the  two  lychrymal  ca- 
nals proceed  to  c,  The  lachrymal  fac.  d,  The 
large  lachrymal  du(T.  e,  Its  opening  into  the 
nofe.  f,  The  caruncula  lachrymalis.  g,  The 
■ eye-ball. 

Fig.  2.  An  interior  View  of  the  Coats  and  Hu- 
mours of  the  Eye. 

a a a a,  The  tunica  fclerotica  cut  in  four  an- 
gles, and  turned  back,  bbbb.  The  tunica  cho- 
roides  adhering  to  the  infide  of  the  fclerotica, 
and  the  ciliary  veffels  are  feen  paffing  over — c c. 
The  retina  which  covers  the  vitreous  humour, 
dd.  The  ciliary  procelTes,  which  were  conti- 
nued from  the  choroid  coat,  e e.  The  iris,  f. 
The  pupil. 

Fig.  3.  Shows  the  Optic  Nerves,  and  Mufcles 
of  the  Eye. 

a a.  The  two  optic  nerves  before  they  meet, 
h,  The  two  optic  nerves  conjoined,  c.  The 


Part  VI.  AND  THEIR  ORGANS.  435 
right  optic  nerve,  d,  Mufculus  attolens  palpe- 
brse  fuperioris.  e,  Attoilens  oculi.  f,  Abduc- 
tor. g g,  Obliquus  fuperior,  or  trochlearis.  h, 
Addudtor.  i,  The  eye-ball. 

Fig.  4.  Shows  the  Eye-balls  with  its  Mufcles. 

a,  The  optic  nerve,  b,  Mufculus  trochlearis, 
c,  Part  of  the  os  frontis,  to  which  the  trochlea 
or  pully  is  fixed,  through  which, — d.  The  ten- 
dons of  the  trochlearis  palfes,  e,  Attoilens  oc^ 
culi.  f,  Addudtor  oculi.  g,  Abdudtor  oculr. 
h,  Obliquus  inferior,  i.  Part  of  the  fuperior 
maxillary  bone  to  which  it  is  fixed,  k,  The 
eye-ball. 

Fig.  5.  Reprefents  the  Nerves  and  Mufcles  of 
the  Right  Eye,  after  part  of  the  Bones  of  the 
orbit  have  been  cut  away. 

A,  The  eye-ball.  B,  The  lachrymal  gland. 
C,  Mufculus  abduftor  oculi.  D,  Attolens.  E, 
Levator  palpebrse  fuperioris.  F,  DeprelTor  oculi. 
G.  Adduftor.  H,  Obliquus  fuperior,  with  its  pul- 
ly.  I,  Its  infertion  into  the  fclerotic  coat.  K, 
Part  of  the  obliquus  inferior.  L,  The  anterior 
part  of  the  os  frontis  cut.  M,  The  crifta  galli 
of  the  ethmoid  bone.  N,  The  pofterior  part  of 
the  fphenoid  bone.  O,  Tranfverfe  fpinous  pro- 
cefs  of  the  fphenoid  bone.  P,  The  carotid  ar- 
tery, denuded  vv^here  it  palfes  through  the  bones. 

Q^,  The 


436  OF  THE  SENSES.  Part  VI. 

Q^,  The  carotid  artery  within  the  cranium. 
R,  The  ocular  artery. 

Nerves — a a,  The  optic  nerve,  b,  The  , 
third  pair. — c,  Its  joining  with  a branch  of  the 
firit  branch  of  the  fifth  pair,  to  form  l,“The  len- 
ticular ganglion,  which  fends  off  the  ciliary 
nerves,  d,  e e,  The  fourth  pair,  f.  The  trunk 
of  the  fifth  pair,  g,  The  firfl  branch  of  the  fifth 
pair,  named  ophthalmic,  h.  The  frontal  branch 
of  it.  i,  Its  ciliary  branches,  along  with  which 
the  nafal  twig  is  fent  to  the  nofe.  k,  Its  branch 
to  the  lachrymal  gland.  1,  The  lenticular  gan- 
glion, m,  The  fecond  branch  of  the  fifth  pair, 
named  fuperior  maxillary,  n.  The  third  branch 
of  the  fifth  pair,  named  inferior  maxillary.  Oj 
The  fixth  pair  of  nerves, — which  fends  off  p, 
The  beginning  of  the  great  fympathetic.  q.  The 
remainder  of  the  fixth  pair,  fpent  on  c.  The  ab- 
dudtor  oculi. 

Fig.  6.  Reprefeiits  the  head  of  a youth,  where 
the  upper  part  of  the  cranium  is  fawed  off, — ^to 
Ihow  the  upper  part  of  the  brain,  covered  by  the 
pia  mater,  the  veffels  of  which  are  minutely 
filled  wdth  wax. 

A A,  The  cut  edges  of  the  upper  part  of  the 
cranium.  B,  The  two  tables  and  intermediate 
diploe.  B B,  The  two  hemifpheres  of  the  ce- 
rebrum. C C,  The  incifure  made  by  the  falx. 
D,  Part  of  the  tentorium  cerebello  fuper  ex- 

panfum. 


Part  VI.  AND  THEIR  ORGANS.  437 
panfum.  E,  Part  of  the  falx,  which  is  fixed  to 
the  crifta  galli. 

Fig.  7.  Reprefents  the  parts  of  the  external 
Ear,  with  the  Parotid  Gland  and  its  Du£ts. 

a a.  The  helix,  b.  The  antihelix,  c.  The 
antitragus,  d.  The  tragus,  e.  The  lobe  of  the 
ear.  f,  The  cavitas  innominata.  g.  The  fcapha. 
h.  The  concha,  ii.  The  parotid  gland,  k,  A 
lymphatic  gland,  which  is  often  found  before 
the  tragus.  1.  The  dud; "of  the  parotic  gland, 
m.  Its  opening  into  the  mouth. 

Eig.  8.  A view  of  the  pofterior  part  of  the  ex- 
ternal ear,  meatus  auditorius,  tyrnpanum^ 
with  its  fmall  bones,  and  Euftachian  tube  of 
the  right  fide. 

a,  The  back  part  of  the  meatus,  with  the 
fmall  ceruminous  glands,  b.  The  incus,  c. 
Malleus,  d.  The  chorda  tympani.  e,  Mem- 
brana  tympani.  f,  Euftachian  tube,  g.  Its 
mouth  from  the  fauces. 

FrG.  9.  Reprefents  the  anterior  part  of  the  right 
external  ear,  the  cavity  of  the  tympanum— 
its  fmall  bones,  cochlea,  and  femicircular  ca- 
nals. 

a,  The  malleus,  b.  Incus  with  its  long  leg, 
refting  upon  the  ftapes.  c,  Membrana  tympani. 

I d e.  The 


438  OF  THE  SENSES,  &c.  Part  VI, 

d,  e,  The  Euftachian  tube,  covered  by  part  of 
— f f,  The  mufculus  circumfiexus  palati.  123, 
The  three  femicircular  canals.  4,  The  veftible. 
5,  The  cochlea.  6,  The  portio  mollis  of  the 
feventh  pair  of  nerves. 

Fig.  10.  Shews  the  mufcles  which  compofe  the 
flefhy  fubftance  of  the  tongue. 

a a.  The  tip  of  the  tongue,  with  fome  of  the 
papillae  minimae.  b,  The  root  of  the  tongue, 
c,  Part  of  the  membrane  of  the  tongue,  which 
covered  the  epiglottis,  d d,  Part  of  the  muf- 
culus hyo-gloffus.  e,  The  lingualis.  f,  Genio- 
gloffus.  g g,  Part  of  the  ftylo-gloffus. 

THE  END. 


DIRECTIONS  FOR  PLACING  the  PLATES. 
Plate  19  to  face  page  138 


20 


144 

158 


23} 

24] 

25 

26  7 

27  j 

28 

29 

30 


236 

320 

326 

378 

404 

438 


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